CVE-2026-31718

{"dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": {"cveId": "CVE-2026-31718", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2026-03-09T15:48:24.134Z", "datePublished": "2026-05-01T13:56:12.680Z", "dateUpdated": "2026-08-05T12:24:49.667Z"}, "containers": {"cna": {"providerMetadata": {"orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T12:24:49.667Z"}, "descriptions": [{"lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger\n\nWhen a durable file handle survives session disconnect (TCP close without\nSMB2_LOGOFF), session_fd_check() sets fp->conn = NULL to preserve the\nhandle for later reconnection. However, it did not clean up the byte-range\nlocks on fp->lock_list.\n\nLater, when the durable scavenger thread times out and calls\n__ksmbd_close_fd(NULL, fp), the lock cleanup loop did:\n\n spin_lock(&fp->conn->llist_lock);\n\nThis caused a slab use-after-free because fp->conn was NULL and the\noriginal connection object had already been freed by\nksmbd_tcp_disconnect().\n\nThe root cause is asymmetric cleanup: lock entries (smb_lock->clist) were\nleft dangling on the freed conn->lock_list while fp->conn was nulled out.\n\nTo fix this issue properly, we need to handle the lifetime of\nsmb_lock->clist across three paths:\n - Safely skip clist deletion when list is empty and fp->conn is NULL.\n - Remove the lock from the old connection's lock_list in\n session_fd_check()\n - Re-add the lock to the new connection's lock_list in\n ksmbd_reopen_durable_fd()."}], "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 - ksmbd is an in-kernel SMB server reachable over TCP/IP, and the vulnerable durable-handle and byte-range-lock paths are driven by SMB2 network requests.\nAC:L - The attacker can create the durable handle, add a lock, disconnect TCP without SMB2_LOGOFF, and wait for the durable scavenger; no race or condition outside attacker control is required.\nPR:N - The path requires an SMB session and tree connection, but ksmbd supports guest/anonymous sessions and guest shares, making a no-credential network attack a reasonable high-severity deployment scenario.\nUI:N - No victim interaction is required once the ksmbd service is exposed; the attacker sends SMB2 requests and closes the connection.\nS:U - The bug corrupts kernel/ksmbd state within the same security authority and does not cross a VM, IOMMU, or sandbox boundary.\nC:H - This is a kernel use-after-free involving dangling list entries tied to freed connection state, and such memory corruption can plausibly be shaped into kernel memory disclosure.\nI:H - The same UAF/list corruption can plausibly be leveraged for kernel memory corruption or control-flow impact, so high integrity impact is warranted.\nA:H - At minimum, triggering the scavenger cleanup can dereference freed or invalid connection/list state and crash the kernel."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/server/vfs_cache.c"], "versions": [{"version": "8df4bcdb0a4232192b2445256c39b787d58ef14d", "lessThan": "0000a7780e0e446a28a273572f6ea8f7f582f694", "status": "affected", "versionType": "git"}, {"version": "c8efcc786146a951091588e5fa7e3c754850cb3c", "lessThan": "e33c65f011980b4ad4abfd93585ec2079856368f", "status": "affected", "versionType": "git"}, {"version": "c8efcc786146a951091588e5fa7e3c754850cb3c", "lessThan": "3d6682726c2d3a46d31dae88b8166786b09b03ad", "status": "affected", "versionType": "git"}, {"version": "c8efcc786146a951091588e5fa7e3c754850cb3c", "lessThan": "b34fc42cfe922e551f7a27d3ac3bb016e41d7dd9", "status": "affected", "versionType": "git"}, {"version": "c8efcc786146a951091588e5fa7e3c754850cb3c", "lessThan": "235e32320a470fcd3998fb3774f2290a0eb302a1", "status": "affected", "versionType": "git"}, {"version": "6.6.32", "lessThan": "6.6.140", "status": "affected", "versionType": "semver"}]}, {"product": "Linux", "vendor": "Linux", "defaultStatus": "affected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/server/vfs_cache.c"], "versions": [{"version": "6.9", "status": "affected"}, {"version": "0", "lessThan": "6.9", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.140", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.84", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.25", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.0.2", "lessThanOrEqual": "7.0.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.1", "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": "6.6.32", "versionEndExcluding": "6.6.140"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "6.12.84"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "6.18.25"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "7.0.2"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "6.9", "versionEndExcluding": "7.1"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/0000a7780e0e446a28a273572f6ea8f7f582f694"}, {"url": "https://git.kernel.org/stable/c/e33c65f011980b4ad4abfd93585ec2079856368f"}, {"url": "https://git.kernel.org/stable/c/3d6682726c2d3a46d31dae88b8166786b09b03ad"}, {"url": "https://git.kernel.org/stable/c/b34fc42cfe922e551f7a27d3ac3bb016e41d7dd9"}, {"url": "https://git.kernel.org/stable/c/235e32320a470fcd3998fb3774f2290a0eb302a1"}], "title": "ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

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However, it did not clean up the byte-range\nlocks on fp->lock_list.\n\nLater, when the durable scavenger thread times out and calls\n__ksmbd_close_fd(NULL, fp), the lock cleanup loop did:\n\n spin_lock(&fp->conn->llist_lock);\n\nThis caused a slab use-after-free because fp->conn was NULL and the\noriginal connection object had already been freed by\nksmbd_tcp_disconnect().\n\nThe root cause is asymmetric cleanup: lock entries (smb_lock->clist) were\nleft dangling on the freed conn->lock_list while fp->conn was nulled out.\n\nTo fix this issue properly, we need to handle the lifetime of\nsmb_lock->clist across three paths:\n - Safely skip clist deletion when list is empty and fp->conn is NULL.\n - Remove the lock from the old connection's lock_list in\n session_fd_check()\n - Re-add the lock to the new connection's lock_list in\n ksmbd_reopen_durable_fd()."}, {"lang": "es", "value": "En el kernel de Linux, la siguiente vulnerabilidad ha sido resuelta:\n\nksmbd: correcci\u00f3n de uso despu\u00e9s de liberaci\u00f3n en __ksmbd_close_fd() a trav\u00e9s del recolector duradero\n\nCuando un manejador de archivo duradero sobrevive a la desconexi\u00f3n de la sesi\u00f3n (cierre TCP sin SMB2_LOGOFF), session_fd_check() establece fp -> conn = NULL para preservar el manejador para una reconexi\u00f3n posterior. Sin embargo, no limpi\u00f3 los bloqueos de rango de bytes en fp -> lock_list.\n\nM\u00e1s tarde, cuando el hilo recolector duradero agota el tiempo de espera y llama a __ksmbd_close_fd(NULL, fp), el bucle de limpieza de bloqueos hizo:\n\n spin_lock(&fp -> conn -> llist_lock);\n\nEsto caus\u00f3 un uso despu\u00e9s de liberaci\u00f3n de slab porque fp -> conn era NULL y el objeto de conexi\u00f3n original ya hab\u00eda sido liberado por ksmbd_tcp_disconnect().\n\nLa causa ra\u00edz es una limpieza asim\u00e9trica: las entradas de bloqueo (smb_lock -> clist) quedaron colgando en la conn -> lock_list liberada mientras fp -> conn se anulaba.\n\nPara corregir este problema correctamente, necesitamos manejar la vida \u00fatil de smb_lock -> clist a trav\u00e9s de tres rutas:\n - Omitir de forma segura la eliminaci\u00f3n de clist cuando la lista est\u00e1 vac\u00eda y fp -> conn es NULL.\n - Eliminar el bloqueo de la lock_list de la conexi\u00f3n antigua en session_fd_check()\n - Volver a a\u00f1adir el bloqueo a la lock_list de la nueva conexi\u00f3n en ksmbd_reopen_durable_fd()."}], "id": "CVE-2026-31718", "lastModified": "2026-11-11T21:10:00.200", "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"}]}, "published": "2026-05-01T14:16:21.963", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "url": "https://git.kernel.org/stable/c/0000a7780e0e446a28a273572f6ea8f7f582f694"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/235e32320a470fcd3998fb3774f2290a0eb302a1"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/3d6682726c2d3a46d31dae88b8166786b09b03ad"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/b34fc42cfe922e551f7a27d3ac3bb016e41d7dd9"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/e33c65f011980b4ad4abfd93585ec2079856368f"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Modified", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: ksmbd: fix use-after-free in __ksmbd_close_fd() via durable scavenger", "id": "2464490", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2464490"}, "csaw": false, "cwe": "CWE-825", "details": ["A flaw was found in ksmbd, the in-kernel SMB3 server for Linux. This vulnerability arises from an asymmetric cleanup process when a durable file handle survives a session disconnect. Specifically, byte-range locks are not properly cleared, leading to a 'use-after-free' error when the durable scavenger thread attempts to access a freed connection object. A remote attacker could exploit this to cause a denial of service or potentially execute arbitrary code."], "name": "CVE-2026-31718", "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": "2026-05-01T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-31718\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-31718\nhttps://lore.kernel.org/linux-cve-announce/2026050124-CVE-2026-31718-5752@gregkh/T"]}

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