CVE-2026-89655

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-89655", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-11T19:38:34.743Z", "datePublished": "2026-09-11T19:45:44.841Z", "dateUpdated": "2026-10-19T08:50:26.879Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:50:26.879Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock\n\nlist_for_each_entry() iterates ci->i_cap_flush_list but drops\ni_ceph_lock to send cap messages. During the unlock window,\nhandle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries\nwith tid <= flush_tid from the list, release i_ceph_lock, and free\nthem via ceph_free_cap_flush() outside any lock. When the original\nthread reacquires i_ceph_lock and the for-loop macro advances via\ncf = list_next_entry(cf, i_list), it dereferences cf->i_list.next\non freed memory.\n\nThe race timeline:\n\n __kick_flushing_caps() handle_cap_flush_ack()\n ----------------------- -----------------------\n holds i_ceph_lock <---\n iterates to cf (tid=10)\n prepares FLUSH message\n drops i_ceph_lock <---\n __send_cap() \u2500\u2500 FLUSH(tid=10)\n\t MDS sends FLUSH_ACK(tid=10)\n ---> acquires i_ceph_lock\n cf->tid(10) <= flush_tid(10),\n detaches cf from i_cap_flush_list\n drops i_ceph_lock\n ceph_free_cap_flush(cf) <- frees it!\n acquires i_ceph_lock <---\n for-loop advances:\n cf = list_next_entry(cf, i_list)\n -- UAF on freed cf->i_list.next\n\nThe cf was just sent by __kick_flushing_caps itself via __send_cap().\nThe MDS may respond with FLUSH_ACK quickly enough that\nhandle_cap_flush_ack() frees cf before __kick_flushing_caps can\nfinish the iteration.\n\nFix by converting to a manual while loop: save the next pointer\nunder i_ceph_lock before dropping it, then use the saved pointer\nafter reacquiring, so the potentially-freed cf is never accessed again."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "baseScore": 9.8, "baseSeverity": "CRITICAL"}, "scenarios": [{"lang": "en", "value": "AV:N - handle_cap_flush_ack() runs in the ceph-msgr kworker on CEPH_MSG_CLIENT_CAPS FLUSH_ACK from the MDS over TCP; a malicious or compromised MDS frees the ceph_cap_flush while __kick_flushing_caps() still holds that pointer after dropping i_ceph_lock to send FLUSH.\nAC:L - The MDS controls both sides of the race: it can induce kicking without s_mutex (reconnect sets CEPH_I_KICK_FLUSH, then delayed ceph_check_caps or revoke-queued writeback) and immediately send FLUSH_ACK for the known flush tid in the unlock window around __send_cap().\nPR:N - The attacker is the remote MDS peer on an already-connected kernel CephFS client and needs no Linux UID, capability, or init-namespace root on the victim, matching other MDS-driven client CVEs such as CVE-2026-89651.\nUI:N - Once CephFS is mounted (standard in Rook/Kubernetes/OpenStack), cap-flush kicking runs from mdsc delayed work and writeback, and FLUSH_ACK is processed automatically in kworker context with no further victim mount or interactive step at exploit time.\nS:U - The use-after-free is of a ceph_cap_flush object in the host kernel heap and stays inside the same kernel security authority; it does not cross a VM, IOMMU, or sandbox boundary.\nC:H - After ceph_free_cap_flush(), __kick_flushing_caps() does list_next_entry() on the freed cf; reclaiming the dedicated ceph_cap_flush slab with attacker-controlled objects yields a fake next pointer and arbitrary kernel read, scored High per UAF guidance.\nI:H - The iterator then treats the sprayed object as a live ceph_cap_flush (tid, caps, is_capsnap, i_list) and continues sending cap state from it, giving a heap-reuse write and control-flow hijack primitive scored High for use-after-free.\nA:H - Dereferencing freed cf->i_list.next oopses or panics the kicker thread even without full exploitation, and a malicious MDS can retrigger the race on every cap flush."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/ceph/caps.c"], "versions": [{"version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "091137821e1fc88f37e15201abf055c9494ddc61", "status": "affected", "versionType": "git"}, {"version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "01542430081014d80fc9e70e92d6647432ddb7fc", "status": "affected", "versionType": "git"}, {"version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "23eb34a53a53cb1a6dab1eeee830633207ac158d", "status": "affected", "versionType": "git"}, {"version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "19f16f04c2b014a7dd214dc1e42557d8530b16f3", "status": "affected", "versionType": "git"}, {"version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "2701431aa3cc8b23efe6890182e7b04f5e76fab5", "status": "affected", "versionType": "git"}, {"version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "fe46746087b5b9c5bb2d022df6c7819218494ced", "status": "affected", "versionType": "git"}, {"version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "2dba24dcd5050be4b7b119e6f0b01f62203b5d26", "status": "affected", "versionType": "git"}, {"version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "7af4c4f01305b0935adf6d4301b1ec407025485d", "status": "affected", "versionType": "git"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/ceph/caps.c"], "versions": [{"version": "4.8", "status": "affected"}, {"version": "0", "lessThan": "4.8", "status": "unaffected", "versionType": "semver"}, {"version": "5.10.270", "lessThanOrEqual": "5.10.*", "status": "unaffected", "versionType": "semver"}, {"version": "5.15.221", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.188", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.157", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.109", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.50", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2.4", "lessThanOrEqual": "7.2.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.3", "lessThanOrEqual": "*", "status": "unaffected", "versionType": "original_commit_for_fix"}]}], "cpeApplicability": [{"nodes": [{"operator": "OR", "negate": false, "cpeMatch": [{"vulnerable": true, "criteria": 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"7.2.4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "4.8", "versionEndExcluding": "7.3"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/091137821e1fc88f37e15201abf055c9494ddc61"}, {"url": "https://git.kernel.org/stable/c/01542430081014d80fc9e70e92d6647432ddb7fc"}, {"url": "https://git.kernel.org/stable/c/23eb34a53a53cb1a6dab1eeee830633207ac158d"}, {"url": "https://git.kernel.org/stable/c/19f16f04c2b014a7dd214dc1e42557d8530b16f3"}, {"url": "https://git.kernel.org/stable/c/2701431aa3cc8b23efe6890182e7b04f5e76fab5"}, {"url": "https://git.kernel.org/stable/c/fe46746087b5b9c5bb2d022df6c7819218494ced"}, {"url": "https://git.kernel.org/stable/c/2dba24dcd5050be4b7b119e6f0b01f62203b5d26"}, {"url": "https://git.kernel.org/stable/c/7af4c4f01305b0935adf6d4301b1ec407025485d"}], "title": "ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-89655", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-10-16T19:25:27.776156Z"}}}], "title": "CISA ADP Vulnrichment", "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:26:47.285Z"}}]}}

{"dataType": "CVE_RECORD", "containers": {"adp": [{"title": "CISA ADP Vulnrichment", "metrics": [{"other": {"type": "ssvc", "content": {"id": "CVE-2026-89655", "role": "CISA Coordinator", "options": [{"Exploitation": "none"}, {"Automatable": "yes"}, {"Technical Impact": "total"}], "version": "2.0.3", "timestamp": "2026-10-16T19:25:27.776156Z"}}}], "providerMetadata": {"orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "shortName": "CISA-ADP", "dateUpdated": "2026-10-16T19:25:28.446Z"}}], "cna": {"title": "ceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock", "metrics": [{"cvssV3_1": {"version": "3.1", "baseScore": 9.8, "baseSeverity": "CRITICAL", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H"}, "scenarios": [{"lang": "en", "value": "AV:N - handle_cap_flush_ack() runs in the ceph-msgr kworker on CEPH_MSG_CLIENT_CAPS FLUSH_ACK from the MDS over TCP; a malicious or compromised MDS frees the ceph_cap_flush while __kick_flushing_caps() still holds that pointer after dropping i_ceph_lock to send FLUSH.\nAC:L - The MDS controls both sides of the race: it can induce kicking without s_mutex (reconnect sets CEPH_I_KICK_FLUSH, then delayed ceph_check_caps or revoke-queued writeback) and immediately send FLUSH_ACK for the known flush tid in the unlock window around __send_cap().\nPR:N - The attacker is the remote MDS peer on an already-connected kernel CephFS client and needs no Linux UID, capability, or init-namespace root on the victim, matching other MDS-driven client CVEs such as CVE-2026-89651.\nUI:N - Once CephFS is mounted (standard in Rook/Kubernetes/OpenStack), cap-flush kicking runs from mdsc delayed work and writeback, and FLUSH_ACK is processed automatically in kworker context with no further victim mount or interactive step at exploit time.\nS:U - The use-after-free is of a ceph_cap_flush object in the host kernel heap and stays inside the same kernel security authority; it does not cross a VM, IOMMU, or sandbox boundary.\nC:H - After ceph_free_cap_flush(), __kick_flushing_caps() does list_next_entry() on the freed cf; reclaiming the dedicated ceph_cap_flush slab with attacker-controlled objects yields a fake next pointer and arbitrary kernel read, scored High per UAF guidance.\nI:H - The iterator then treats the sprayed object as a live ceph_cap_flush (tid, caps, is_capsnap, i_list) and continues sending cap state from it, giving a heap-reuse write and control-flow hijack primitive scored High for use-after-free.\nA:H - Dereferencing freed cf->i_list.next oopses or panics the kicker thread even without full exploitation, and a malicious MDS can retrigger the race on every cap flush."}]}], "affected": [{"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "091137821e1fc88f37e15201abf055c9494ddc61", "versionType": "git"}, {"status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "01542430081014d80fc9e70e92d6647432ddb7fc", "versionType": "git"}, {"status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "23eb34a53a53cb1a6dab1eeee830633207ac158d", "versionType": "git"}, {"status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "19f16f04c2b014a7dd214dc1e42557d8530b16f3", "versionType": "git"}, {"status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "2701431aa3cc8b23efe6890182e7b04f5e76fab5", "versionType": "git"}, {"status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "fe46746087b5b9c5bb2d022df6c7819218494ced", "versionType": "git"}, {"status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "2dba24dcd5050be4b7b119e6f0b01f62203b5d26", "versionType": "git"}, {"status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "lessThan": "7af4c4f01305b0935adf6d4301b1ec407025485d", "versionType": "git"}], "programFiles": ["fs/ceph/caps.c"], "defaultStatus": "unaffected"}, {"repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "product": "Linux", "versions": [{"status": "affected", "version": "4.8"}, {"status": "unaffected", "version": "0", "lessThan": "4.8", "versionType": "semver"}, {"status": "unaffected", "version": "5.10.270", "versionType": "semver", "lessThanOrEqual": "5.10.*"}, {"status": "unaffected", "version": "5.15.221", "versionType": "semver", "lessThanOrEqual": "5.15.*"}, {"status": "unaffected", "version": "6.1.188", "versionType": "semver", "lessThanOrEqual": "6.1.*"}, {"status": "unaffected", "version": "6.6.157", "versionType": "semver", "lessThanOrEqual": "6.6.*"}, {"status": "unaffected", "version": "6.12.109", "versionType": "semver", "lessThanOrEqual": "6.12.*"}, {"status": "unaffected", "version": "6.18.50", "versionType": "semver", "lessThanOrEqual": "6.18.*"}, {"status": "unaffected", "version": "7.2.4", "versionType": "semver", "lessThanOrEqual": "7.2.*"}, {"status": "unaffected", "version": "7.3", "versionType": "original_commit_for_fix", "lessThanOrEqual": "*"}], "programFiles": ["fs/ceph/caps.c"], "defaultStatus": "affected"}], "references": [{"url": "https://git.kernel.org/stable/c/091137821e1fc88f37e15201abf055c9494ddc61"}, {"url": "https://git.kernel.org/stable/c/01542430081014d80fc9e70e92d6647432ddb7fc"}, {"url": "https://git.kernel.org/stable/c/23eb34a53a53cb1a6dab1eeee830633207ac158d"}, {"url": "https://git.kernel.org/stable/c/19f16f04c2b014a7dd214dc1e42557d8530b16f3"}, {"url": "https://git.kernel.org/stable/c/2701431aa3cc8b23efe6890182e7b04f5e76fab5"}, {"url": "https://git.kernel.org/stable/c/fe46746087b5b9c5bb2d022df6c7819218494ced"}, {"url": "https://git.kernel.org/stable/c/2dba24dcd5050be4b7b119e6f0b01f62203b5d26"}, {"url": "https://git.kernel.org/stable/c/7af4c4f01305b0935adf6d4301b1ec407025485d"}], "x_generator": {"engine": "bippy-1.2.0"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock\n\nlist_for_each_entry() iterates ci->i_cap_flush_list but drops\ni_ceph_lock to send cap messages. During the unlock window,\nhandle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries\nwith tid <= flush_tid from the list, release i_ceph_lock, and free\nthem via ceph_free_cap_flush() outside any lock. When the original\nthread reacquires i_ceph_lock and the for-loop macro advances via\ncf = list_next_entry(cf, i_list), it dereferences cf->i_list.next\non freed memory.\n\nThe race timeline:\n\n __kick_flushing_caps() handle_cap_flush_ack()\n ----------------------- -----------------------\n holds i_ceph_lock <---\n iterates to cf (tid=10)\n prepares FLUSH message\n drops i_ceph_lock <---\n __send_cap() \u2500\u2500 FLUSH(tid=10)\n\t MDS sends FLUSH_ACK(tid=10)\n ---> acquires i_ceph_lock\n cf->tid(10) <= flush_tid(10),\n detaches cf from i_cap_flush_list\n drops i_ceph_lock\n ceph_free_cap_flush(cf) <- frees it!\n acquires i_ceph_lock <---\n for-loop advances:\n cf = list_next_entry(cf, i_list)\n -- UAF on freed cf->i_list.next\n\nThe cf was just sent by __kick_flushing_caps itself via __send_cap().\nThe MDS may respond with FLUSH_ACK quickly enough that\nhandle_cap_flush_ack() frees cf before __kick_flushing_caps can\nfinish the iteration.\n\nFix by converting to a manual while loop: save the next pointer\nunder i_ceph_lock before dropping it, then use the saved pointer\nafter reacquiring, so the potentially-freed cf is never accessed again."}], "cpeApplicability": [{"nodes": [{"negate": false, "cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.10.270", "versionStartIncluding": "4.8"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "5.15.221", "versionStartIncluding": "4.8"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.1.188", "versionStartIncluding": "4.8"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.6.157", "versionStartIncluding": "4.8"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.12.109", "versionStartIncluding": "4.8"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "6.18.50", "versionStartIncluding": "4.8"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "7.2.4", "versionStartIncluding": "4.8"}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "vulnerable": true, "versionEndExcluding": "7.3", "versionStartIncluding": "4.8"}], "operator": "OR"}]}], "providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-19T08:50:26.879Z"}}}, "cveMetadata": {"cveId": "CVE-2026-89655", "state": "PUBLISHED", "dateUpdated": "2026-10-19T08:50:26.879Z", "dateReserved": "2026-09-11T19:38:34.743Z", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "datePublished": "2026-09-11T19:45:44.841Z", "assignerShortName": "Linux"}, "dataVersion": "5.2"}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["fs/ceph/caps.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "091137821e1fc88f37e15201abf055c9494ddc61", "status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "versionType": "git"}, {"lessThan": "01542430081014d80fc9e70e92d6647432ddb7fc", "status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "versionType": "git"}, {"lessThan": "23eb34a53a53cb1a6dab1eeee830633207ac158d", "status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "versionType": "git"}, {"lessThan": "19f16f04c2b014a7dd214dc1e42557d8530b16f3", "status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "versionType": "git"}, {"lessThan": "2701431aa3cc8b23efe6890182e7b04f5e76fab5", "status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "versionType": "git"}, {"lessThan": "fe46746087b5b9c5bb2d022df6c7819218494ced", "status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "versionType": "git"}, {"lessThan": "2dba24dcd5050be4b7b119e6f0b01f62203b5d26", "status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "versionType": "git"}, {"lessThan": "7af4c4f01305b0935adf6d4301b1ec407025485d", "status": "affected", "version": "e4500b5e35c213e0f97be7cb69328c0877203a79", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["fs/ceph/caps.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "4.8"}, {"lessThan": "4.8", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "5.10.*", "status": "unaffected", "version": "5.10.270", "versionType": "semver"}, {"lessThanOrEqual": "5.15.*", "status": "unaffected", "version": "5.15.221", "versionType": "semver"}, {"lessThanOrEqual": "6.1.*", "status": "unaffected", "version": "6.1.188", "versionType": "semver"}, {"lessThanOrEqual": "6.6.*", "status": "unaffected", "version": "6.6.157", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.109", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.50", "versionType": "semver"}, {"lessThanOrEqual": "7.2.*", "status": "unaffected", "version": "7.2.4", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "7.3", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nceph: fix UAF in __kick_flushing_caps() on cf entry freed during unlock\n\nlist_for_each_entry() iterates ci->i_cap_flush_list but drops\ni_ceph_lock to send cap messages. During the unlock window,\nhandle_cap_flush_ack() can acquire i_ceph_lock, detach cf entries\nwith tid <= flush_tid from the list, release i_ceph_lock, and free\nthem via ceph_free_cap_flush() outside any lock. When the original\nthread reacquires i_ceph_lock and the for-loop macro advances via\ncf = list_next_entry(cf, i_list), it dereferences cf->i_list.next\non freed memory.\n\nThe race timeline:\n\n __kick_flushing_caps() handle_cap_flush_ack()\n ----------------------- -----------------------\n holds i_ceph_lock <---\n iterates to cf (tid=10)\n prepares FLUSH message\n drops i_ceph_lock <---\n __send_cap() \u2500\u2500 FLUSH(tid=10)\n\t MDS sends FLUSH_ACK(tid=10)\n ---> acquires i_ceph_lock\n cf->tid(10) <= flush_tid(10),\n detaches cf from i_cap_flush_list\n drops i_ceph_lock\n ceph_free_cap_flush(cf) <- frees it!\n acquires i_ceph_lock <---\n for-loop advances:\n cf = list_next_entry(cf, i_list)\n -- UAF on freed cf->i_list.next\n\nThe cf was just sent by __kick_flushing_caps itself via __send_cap().\nThe MDS may respond with FLUSH_ACK quickly enough that\nhandle_cap_flush_ack() frees cf before __kick_flushing_caps can\nfinish the iteration.\n\nFix by converting to a manual while loop: save the next pointer\nunder i_ceph_lock before dropping it, then use the saved pointer\nafter reacquiring, so the potentially-freed cf is never accessed again."}], "id": "CVE-2026-89655", "lastModified": "2026-10-19T09:18:03.187", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 9.8, "baseSeverity": "CRITICAL", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-89655", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "total"}], "role": "CISA Coordinator", "timestamp": "2026-10-16T19:25:27.776156Z", "version": "2.0.3"}}]}, "published": "2026-09-11T20:19:51.683", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/01542430081014d80fc9e70e92d6647432ddb7fc"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/091137821e1fc88f37e15201abf055c9494ddc61"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/19f16f04c2b014a7dd214dc1e42557d8530b16f3"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/23eb34a53a53cb1a6dab1eeee830633207ac158d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/2701431aa3cc8b23efe6890182e7b04f5e76fab5"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/2dba24dcd5050be4b7b119e6f0b01f62203b5d26"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/7af4c4f01305b0935adf6d4301b1ec407025485d"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/fe46746087b5b9c5bb2d022df6c7819218494ced"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: ceph: Linux kernel Ceph: Use-After-Free vulnerability in capability message handling", "id": "2532127", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2532127"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.3", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:L/A:H", "status": "draft"}, "cwe": "CWE-366", "details": ["A flaw was found in the Linux kernel's Ceph file system component. A race condition exists in the `__kick_flushing_caps()` function during the handling of capability messages. This allows a separate process to free a data structure (`cf entry`) while `__kick_flushing_caps()` is still iterating over it. This use-after-free (UAF) vulnerability can lead to system instability, a denial of service (DoS), or potentially privilege escalation for a local attacker."], "name": "CVE-2026-89655", "public_date": "2026-09-11T19:45:44Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-89655\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-89655\nhttps://git.kernel.org/stable/c/2701431aa3cc8b23efe6890182e7b04f5e76fab5\nhttps://git.kernel.org/stable/c/2dba24dcd5050be4b7b119e6f0b01f62203b5d26\nhttps://git.kernel.org/stable/c/7af4c4f01305b0935adf6d4301b1ec407025485d\nhttps://git.kernel.org/stable/c/fe46746087b5b9c5bb2d022df6c7819218494ced"], "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,2701431aa3cc8b23efe6890182e7b04f5e76fab5)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,fe46746087b5b9c5bb2d022df6c7819218494ced)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,2dba24dcd5050be4b7b119e6f0b01f62203b5d26)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[1da177e4c3f41524e886b7f1b8a0c1fc7321cac2,7af4c4f01305b0935adf6d4301b1ec407025485d)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,6.12.109)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,6.18.50)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,7.2.4)"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.12.109,6.13.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.18.50,6.19.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[7.2.4,7.3.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "generic", "value": "[7.3-rc1,*]"}}], "enrichment": {"confidence": 99.0, "confidence_source": "inferred", "scores": [{"score": 99.0, "source": "inferred"}, {"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}], "created": "2026-09-12T05:00:08.298557+00:00", "updated": "2026-09-15T21:00:17.859015+00:00", "vendors": ["linux", "linux$PRODUCT$linux_kernel"]}