CVE-2026-98991

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-98991", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-09-25T10:25:14.384Z", "datePublished": "2026-10-23T12:20:10.289Z", "dateUpdated": "2026-10-24T14:09:52.901Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-10-24T14:09:52.901Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nnamespace: queue a mount only once for mount notifications\n\nmnt_notify_add() puts a mount on notify_list. It doesn't check whether\nthe mount is on the list already. That's fine as long as every mount is\nqueued at most once per namespace_sem hold. It isn't.\n\npropagate_umount() moves a surviving overmount off a stack of mounts\nthat are going away and queues it as moved. shrink_submounts() and\nmark_mounts_for_expiry() call umount_tree() for several mounts under a\nsingle namespace_sem hold. So the second umount_tree() can take down\nexactly the mount the first one reparented, reparent it once more and so\nend up queueing it a second time.\n\nThe second list_add_tail() cuts the mounts queued in between out of the\nlist while the head still points at the last of them. notify_mnt_list()\nthen only visits that one mount and the others are freed after the grace\nperiod with notify_list still pointing at them. Every later mount\noperation on the host walks freed memory:\n\n BUG: KASAN: slab-use-after-free in __list_add_valid_or_report\n Read of size 8 at addr ffff8881003d57e0 by task notify_dq/162\n __list_add_valid_or_report+0x15c/0x1a0\n mnt_add_to_ns+0x322/0x890\n attach_recursive_mnt.isra.0+0xf2a/0x1a00\n path_mount+0x139c/0x1d40\n\nThis needs a mount with MNT_SHRINKABLE to bind from. That's what\nfinish_automount() creates (submounts of NFS, AFS and CIFS and the\ntracefs mount below debugfs). Bind mounts inherit the flag. A mount\nnamespace with a FAN_MARK_MNTNS mark does the rest and root in a user\nnamespace can have both.\n\nInitialize to_notify in alloc_vfsmnt() and leave a mount alone that is\nqueued already. mnt_notify() looks at the state the mount has when the\nlist is drained so a single entry per mount is enough. The move event\nfor a mount that is unmounted under the same hold is lost. That's fine.\nThe detach is what matters."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 7.8, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:L - Local umount(2) follows ksys_umount()->path_umount()->do_umount()->shrink_submounts()->umount_tree()->propagate_umount()->reparent()->mnt_notify_add(), the function patched; no network protocol supplies the triggering mount topology.\nAC:L - With a reachable MNT_SHRINKABLE automount, the attacker can create the required bind, shared/slave, and overmount topology and synchronously unmount it; duplicate queueing occurs sequentially under one namespace_sem hold and requires no race.\nPR:L - may_mount() and FAN_MARK_MNTNS use CAP_SYS_ADMIN relative to the attacker-owned mount/group/target user namespaces; unshare(CLONE_NEWUSER|CLONE_NEWNS) gives an ordinary local user those namespace-scoped capabilities without init-namespace privilege.\nUI:N - The attacker personally creates the fanotify mark and mount topology and invokes umount(2); no victim must mount media, open a file, or perform another action.\nS:U - The corrupted global notify_list and freed struct mount objects are resources of the same host kernel reached by the attacker; this is a kernel privilege-escalation boundary, not a guest-host, IOMMU, or other scope change.\nC:H - notify_mnt_list() leaves notify_list linked through freed struct mount::to_notify nodes, so later mount operations dereference attacker-reclaimable mnt_cache objects; this kernel-heap UAF can be leveraged to disclose kernel memory.\nI:H - After the stale to_notify node is freed or reallocated, __list_add() in mnt_notify_add() writes next->prev and prev->next through the corrupted list links, providing exploitable kernel-heap corruption capable of control-flow hijacking.\nA:H - namespace_unlock() frees mounts still referenced by notify_list, and a later path_mount()->mnt_add_to_ns()->mnt_notify_add() provably reads the freed node, producing the documented KASAN slab-use-after-free and a host kernel oops or panic."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/mount.h", "fs/namespace.c"], "versions": [{"version": "bf630c40164162ba1d3933c2f5e3397d083e0948", "lessThan": "acbe9e4418e2ef7bef1a12e62e0e7d6145a15190", "status": "affected", "versionType": "git"}, {"version": "bf630c40164162ba1d3933c2f5e3397d083e0948", "lessThan": "702ff3fe499876e09c45558a05366d21a5bc41ab", "status": "affected", "versionType": "git"}, {"version": "bf630c40164162ba1d3933c2f5e3397d083e0948", "lessThan": "bd2feb7796b6585938a4241e7b7c4148a6f7b762", "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/mount.h", "fs/namespace.c"], "versions": [{"version": "6.15", "status": "affected"}, {"version": "0", "lessThan": "6.15", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.57", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2.11", "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": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "6.18.57"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "7.2.11"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.15", "versionEndExcluding": "7.3"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/acbe9e4418e2ef7bef1a12e62e0e7d6145a15190"}, {"url": "https://git.kernel.org/stable/c/702ff3fe499876e09c45558a05366d21a5bc41ab"}, {"url": "https://git.kernel.org/stable/c/bd2feb7796b6585938a4241e7b7c4148a6f7b762"}], "title": "namespace: queue a mount only once for mount notifications", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["fs/mount.h", "fs/namespace.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "acbe9e4418e2ef7bef1a12e62e0e7d6145a15190", "status": "affected", "version": "bf630c40164162ba1d3933c2f5e3397d083e0948", "versionType": "git"}, {"lessThan": "702ff3fe499876e09c45558a05366d21a5bc41ab", "status": "affected", "version": "bf630c40164162ba1d3933c2f5e3397d083e0948", "versionType": "git"}, {"lessThan": "bd2feb7796b6585938a4241e7b7c4148a6f7b762", "status": "affected", "version": "bf630c40164162ba1d3933c2f5e3397d083e0948", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["fs/mount.h", "fs/namespace.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "6.15"}, {"lessThan": "6.15", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.18.*", "status": "unaffected", "version": "6.18.57", "versionType": "semver"}, {"lessThanOrEqual": "7.2.*", "status": "unaffected", "version": "7.2.11", "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\nnamespace: queue a mount only once for mount notifications\n\nmnt_notify_add() puts a mount on notify_list. It doesn't check whether\nthe mount is on the list already. That's fine as long as every mount is\nqueued at most once per namespace_sem hold. It isn't.\n\npropagate_umount() moves a surviving overmount off a stack of mounts\nthat are going away and queues it as moved. shrink_submounts() and\nmark_mounts_for_expiry() call umount_tree() for several mounts under a\nsingle namespace_sem hold. So the second umount_tree() can take down\nexactly the mount the first one reparented, reparent it once more and so\nend up queueing it a second time.\n\nThe second list_add_tail() cuts the mounts queued in between out of the\nlist while the head still points at the last of them. notify_mnt_list()\nthen only visits that one mount and the others are freed after the grace\nperiod with notify_list still pointing at them. Every later mount\noperation on the host walks freed memory:\n\n BUG: KASAN: slab-use-after-free in __list_add_valid_or_report\n Read of size 8 at addr ffff8881003d57e0 by task notify_dq/162\n __list_add_valid_or_report+0x15c/0x1a0\n mnt_add_to_ns+0x322/0x890\n attach_recursive_mnt.isra.0+0xf2a/0x1a00\n path_mount+0x139c/0x1d40\n\nThis needs a mount with MNT_SHRINKABLE to bind from. That's what\nfinish_automount() creates (submounts of NFS, AFS and CIFS and the\ntracefs mount below debugfs). Bind mounts inherit the flag. A mount\nnamespace with a FAN_MARK_MNTNS mark does the rest and root in a user\nnamespace can have both.\n\nInitialize to_notify in alloc_vfsmnt() and leave a mount alone that is\nqueued already. mnt_notify() looks at the state the mount has when the\nlist is drained so a single entry per mount is enough. The move event\nfor a mount that is unmounted under the same hold is lost. That's fine.\nThe detach is what matters."}], "id": "CVE-2026-98991", "lastModified": "2026-10-24T14:16:51.117", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 7.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}]}, "published": "2026-10-23T13:17:21.137", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/702ff3fe499876e09c45558a05366d21a5bc41ab"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/acbe9e4418e2ef7bef1a12e62e0e7d6145a15190"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/bd2feb7796b6585938a4241e7b7c4148a6f7b762"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Received"}

{"bugzilla": {"description": "kernel: namespace: queue a mount only once for mount notifications", "id": "2559752", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2559752"}, "csaw": false, "cvss3": {"cvss3_base_score": "4.7", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "cwe": "CWE-825", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nnamespace: queue a mount only once for mount notifications\nmnt_notify_add() puts a mount on notify_list. It doesn't check whether\nthe mount is on the list already. That's fine as long as every mount is\nqueued at most once per namespace_sem hold. It isn't.\npropagate_umount() moves a surviving overmount off a stack of mounts\nthat are going away and queues it as moved. shrink_submounts() and\nmark_mounts_for_expiry() call umount_tree() for several mounts under a\nsingle namespace_sem hold. So the second umount_tree() can take down\nexactly the mount the first one reparented, reparent it once more and so\nend up queueing it a second time.\nThe second list_add_tail() cuts the mounts queued in between out of the\nlist while the head still points at the last of them. notify_mnt_list()\nthen only visits that one mount and the others are freed after the grace\nperiod with notify_list still pointing at them. Every later mount\noperation on the host walks freed memory:\nBUG: KASAN: slab-use-after-free in __list_add_valid_or_report\nRead of size 8 at addr ffff8881003d57e0 by task notify_dq/162\n__list_add_valid_or_report+0x15c/0x1a0\nmnt_add_to_ns+0x322/0x890\nattach_recursive_mnt.isra.0+0xf2a/0x1a00\npath_mount+0x139c/0x1d40\nThis needs a mount with MNT_SHRINKABLE to bind from. That's what\nfinish_automount() creates (submounts of NFS, AFS and CIFS and the\ntracefs mount below debugfs). Bind mounts inherit the flag. A mount\nnamespace with a FAN_MARK_MNTNS mark does the rest and root in a user\nnamespace can have both.\nInitialize to_notify in alloc_vfsmnt() and leave a mount alone that is\nqueued already. mnt_notify() looks at the state the mount has when the\nlist is drained so a single entry per mount is enough. The move event\nfor a mount that is unmounted under the same hold is lost. That's fine.\nThe detach is what matters.", "A flaw was found in the Linux kernel. A local attacker can cause a Denial of Service (DoS) by triggering a use-after-free flaw, which occurs when the system accesses memory after it has been released. During certain unmount operations, the kernel fails to verify whether a filesystem mount is already queued for notifications, allowing duplicate entries that leave references to freed memory. Subsequent mount operations traverse this invalid memory, leading to kernel memory corruption and a system crash."], "name": "CVE-2026-98991", "package_state": [{"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 10"}, {"cpe": "cpe:/o:redhat:enterprise_linux:6", "fix_state": "Out of support scope", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 6"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:7", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 7"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:8", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 8"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/o:redhat:enterprise_linux:9", "fix_state": "Not affected", "package_name": "kernel-rt", "product_name": "Red Hat Enterprise Linux 9"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Not affected", "package_name": "openshift/ose-rhel-coreos-8", "product_name": "Red Hat OpenShift Container Platform 4"}, {"cpe": "cpe:/a:redhat:openshift:4", "fix_state": "Not affected", "package_name": "openshift/ose-rhel-coreos-9", "product_name": "Red Hat OpenShift Container Platform 4"}], "public_date": "2026-10-23T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-98991\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-98991\nhttps://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98991.mbox"], "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[bf630c40164162ba1d3933c2f5e3397d083e0948,acbe9e4418e2ef7bef1a12e62e0e7d6145a15190)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[bf630c40164162ba1d3933c2f5e3397d083e0948,702ff3fe499876e09c45558a05366d21a5bc41ab)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[bf630c40164162ba1d3933c2f5e3397d083e0948,bd2feb7796b6585938a4241e7b7c4148a6f7b762)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "6.15"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[0,6.15)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.18.57,6.19.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[7.2.11,7.3.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[7.3,*]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[bf630c40164162ba1d3933c2f5e3397d083e0948,acbe9e4418e2ef7bef1a12e62e0e7d6145a15190)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[bf630c40164162ba1d3933c2f5e3397d083e0948,702ff3fe499876e09c45558a05366d21a5bc41ab)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "code_commit", "value": "[bf630c40164162ba1d3933c2f5e3397d083e0948,bd2feb7796b6585938a4241e7b7c4148a6f7b762)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}, {"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "6.15"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[0,6.15)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[6.18.57,6.19.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[7.2.11,7.3.0)"}}, {"platform": null, "status": "unaffected", "versions": {"scheme": "semver", "value": "[7.3,*]"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "Linux", "source": "cna", "vendor": "Linux"}, "product": "linux_kernel", "vendor": "linux"}], "created": "2026-10-23T15:00:13.038250+00:00", "title": "Kernel Mount Notification Use\u2011After\u2011Free Vulnerability", "updated": "2026-10-29T14:15:07.597870+00:00", "vendors": ["linux", "linux$PRODUCT$linux", "linux$PRODUCT$linux_kernel"], "weaknesses": ["CWE-416", "CWE-825"]}