CVE-2025-21955

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ksmbd is the in-kernel SMB server listening on TCP/445; the entire path (oplock grant, oplock break trigger, and the connection reset that wins the race) is driven purely by SMB2 traffic from remote clients.\nAC:L - The attacker owns both sides of the race \u2014 connection A holds the oplock, connection B triggers the break notification, and the attacker chooses exactly when to reset A's socket \u2014 and can retry the sequence unlimited times over the network.\nPR:L - Reaching an oplock/lease break requires an established SMB2 session and tree connect (SMB2_CREATE with an oplock or lease context), so valid low-privileged share credentials (or a guest mapping) are needed; it is not a pre-authentication code path.\nUI:N - No victim action is required \u2014 the attacker's own two connections create the oplock, trigger the break, and tear down the connection entirely on their own schedule.\nS:U - The use-after-free is confined to kernel memory within the same security authority; no VM, IOMMU, or sandbox boundary is crossed.\nC:H - The freed ksmbd_conn/tcp_transport objects are dereferenced after release, and reclaiming those kmalloc-64 slots with attacker-sprayed data yields a read primitive over kernel memory and leaks server/session state.\nI:H - ksmbd_conn_write() performs an indirect call through conn->transport->ops->writev read out of the freed transport, giving control-flow hijack and arbitrary-write potential once the slab is reclaimed with controlled contents.\nA:H - Even without successful grooming the stale dereference of the freed connection, transport, and released socket reliably oopses or panics the kernel, killing the SMB server host."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/server/connection.c", "fs/smb/server/connection.h", "fs/smb/server/oplock.c", "fs/smb/server/server.c"], "versions": [{"version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "lessThan": "8e6508c7ecb1802909f294827eff38f301d0c937", "status": "affected", "versionType": "git"}, {"version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "lessThan": "09aeab68033161cb54f194da93e51a11aee6144b", "status": "affected", "versionType": "git"}, {"version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "lessThan": "a4261bbc33fbf99b99c80aa3a2c5097611802980", "status": "affected", "versionType": "git"}, {"version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "lessThan": "f17d1c63a76b0fe8e9c78023a86507a3a6d62cfa", "status": "affected", "versionType": "git"}, {"version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "lessThan": "3aa660c059240e0c795217182cf7df32909dd917", "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/smb/server/connection.c", "fs/smb/server/connection.h", "fs/smb/server/oplock.c", "fs/smb/server/server.c"], "versions": [{"version": "5.15", "status": "affected"}, {"version": "0", "lessThan": "5.15", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.191", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.84", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.20", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.13.8", "lessThanOrEqual": "6.13.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.14", "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": "5.15", "versionEndExcluding": "6.1.191"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.6.84"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.12.20"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.13.8"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.14"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/8e6508c7ecb1802909f294827eff38f301d0c937"}, {"url": "https://git.kernel.org/stable/c/09aeab68033161cb54f194da93e51a11aee6144b"}, {"url": "https://git.kernel.org/stable/c/a4261bbc33fbf99b99c80aa3a2c5097611802980"}, {"url": "https://git.kernel.org/stable/c/f17d1c63a76b0fe8e9c78023a86507a3a6d62cfa"}, {"url": "https://git.kernel.org/stable/c/3aa660c059240e0c795217182cf7df32909dd917"}], "title": "ksmbd: prevent connection release during oplock break notification", "x_generator": {"engine": "bippy-1.2.0"}}}}

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{"affected": [{"affectedData": [{"defaultStatus": "unaffected", "product": "Linux", "programFiles": ["fs/smb/server/connection.c", "fs/smb/server/connection.h", "fs/smb/server/oplock.c", "fs/smb/server/server.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"lessThan": "8e6508c7ecb1802909f294827eff38f301d0c937", "status": "affected", "version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "versionType": "git"}, {"lessThan": "09aeab68033161cb54f194da93e51a11aee6144b", "status": "affected", "version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "versionType": "git"}, {"lessThan": "a4261bbc33fbf99b99c80aa3a2c5097611802980", "status": "affected", "version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "versionType": "git"}, {"lessThan": "f17d1c63a76b0fe8e9c78023a86507a3a6d62cfa", "status": "affected", "version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "versionType": "git"}, {"lessThan": "3aa660c059240e0c795217182cf7df32909dd917", "status": "affected", "version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "versionType": "git"}]}, {"defaultStatus": "affected", "product": "Linux", "programFiles": ["fs/smb/server/connection.c", "fs/smb/server/connection.h", "fs/smb/server/oplock.c", "fs/smb/server/server.c"], "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "vendor": "Linux", "versions": [{"status": "affected", "version": "5.15"}, {"lessThan": "5.15", "status": "unaffected", "version": "0", "versionType": "semver"}, {"lessThanOrEqual": "6.1.*", "status": "unaffected", "version": "6.1.191", "versionType": "semver"}, {"lessThanOrEqual": "6.6.*", "status": "unaffected", "version": "6.6.84", "versionType": "semver"}, {"lessThanOrEqual": "6.12.*", "status": "unaffected", "version": "6.12.20", "versionType": "semver"}, {"lessThanOrEqual": "6.13.*", "status": "unaffected", "version": "6.13.8", "versionType": "semver"}, {"lessThanOrEqual": "*", "status": "unaffected", "version": "6.14", "versionType": "original_commit_for_fix"}]}], "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67"}], "configurations": [{"nodes": [{"cpeMatch": [{"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "107B8EDA-32AA-4F44-9637-99D648133FCA", "versionEndExcluding": "6.6.84", "versionStartIncluding": "5.15", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "60E9C5DF-D778-4572-848A-5D6CFFE022CA", "versionEndExcluding": "6.12.20", "versionStartIncluding": "6.7", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "matchCriteriaId": "0A20D4D7-B329-4C68-B662-76062EA7DCF0", "versionEndExcluding": "6.13.8", "versionStartIncluding": "6.13", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc1:*:*:*:*:*:*", "matchCriteriaId": "186716B6-2B66-4BD0-852E-D48E71C0C85F", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc2:*:*:*:*:*:*", "matchCriteriaId": "0D3E781C-403A-498F-9DA9-ECEE50F41E75", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc3:*:*:*:*:*:*", "matchCriteriaId": "66619FB8-0AAF-4166-B2CF-67B24143261D", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc4:*:*:*:*:*:*", "matchCriteriaId": "D3D6550E-6679-4560-902D-AF52DCFE905B", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc5:*:*:*:*:*:*", "matchCriteriaId": "45B90F6B-BEC7-4D4E-883A-9DBADE021750", "vulnerable": true}, {"criteria": "cpe:2.3:o:linux:linux_kernel:6.14:rc6:*:*:*:*:*:*", "matchCriteriaId": "1759FFB7-531C-41B1-9AE1-FD3D80E0D920", "vulnerable": true}], "negate": false, "operator": "OR"}]}], "cveTags": [], "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: prevent connection release during oplock break notification\n\nksmbd_work could be freed when after connection release.\nIncrement r_count of ksmbd_conn to indicate that requests\nare not finished yet and to not release the connection."}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: ksmbd: impide la liberaci\u00f3n de la conexi\u00f3n durante la notificaci\u00f3n de interrupci\u00f3n del bloqueo de oplock. ksmbd_work podr\u00eda liberarse despu\u00e9s de la liberaci\u00f3n de la conexi\u00f3n. Incremente r_count de ksmbd_conn para indicar que las solicitudes a\u00fan no han finalizado y para no liberar la conexi\u00f3n."}], "id": "CVE-2025-21955", "lastModified": "2026-10-30T13:17:54.560", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 8.8, "baseSeverity": "HIGH", "confidentialityImpact": "HIGH", "integrityImpact": "HIGH", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 5.9, "source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "type": "Secondary"}, {"cvssData": {"attackComplexity": "LOW", "attackVector": "LOCAL", "availabilityImpact": "HIGH", "baseScore": 5.5, "baseSeverity": "MEDIUM", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 1.8, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}]}, "published": "2025-04-01T16:15:26.710", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/09aeab68033161cb54f194da93e51a11aee6144b"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/3aa660c059240e0c795217182cf7df32909dd917"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/8e6508c7ecb1802909f294827eff38f301d0c937"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a4261bbc33fbf99b99c80aa3a2c5097611802980"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f17d1c63a76b0fe8e9c78023a86507a3a6d62cfa"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "NVD-CWE-noinfo"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: ksmbd: prevent connection release during oplock break notification", "id": "2356623", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2356623"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.5", "cvss3_scoring_vector": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H", "status": "draft"}, "details": ["In the Linux kernel, the following vulnerability has been resolved:\nksmbd: prevent connection release during oplock break notification\nksmbd_work could be freed when after connection release.\nIncrement r_count of ksmbd_conn to indicate that requests\nare not finished yet and to not release the connection."], "name": "CVE-2025-21955", "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": "Not affected", "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"}], "public_date": "2025-04-01T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-21955\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-21955\nhttps://lore.kernel.org/linux-cve-announce/2025040143-CVE-2025-21955-c393@gregkh/T"], "threat_severity": "Low"}

{}