CVE-2026-64396

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The cancel\ncallback smb2_remove_blocked_lock() holds a reference to the flock.\n\nIf the lock waiter is subsequently woken up but the work state is no\nlonger KSMBD_WORK_ACTIVE (e.g., due to a concurrent cancellation), the\ncleanup path calls locks_free_lock(flock) without dequeuing the work from\nthe async_requests list. Concurrently, smb2_cancel() walks the list\nunder conn->request_lock and invokes the cancel callback, which then\ndereferences the already freed 'flock'. This leads to a slab-use-after-free\ninside __wake_up_common.\n\nFix this by restructuring the cleanup logic after the worker returns\nfrom ksmbd_vfs_posix_lock_wait(). Move list_del(&smb_lock->llist) and\nrelease_async_work(work) to the top of the cleanup block. This guarantees\nthat the async work is completely dequeued and serialized under\nconn->request_lock before locks_free_lock(flock) is called, rendering\nthe flock unreachable for any concurrent smb2_cancel()."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H", "baseScore": 8.8, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:N - ksmbd accepts remote SMB traffic over TCP port 445, and SMB2 LOCK, CLOSE, and CANCEL requests reach the vulnerable code through the network handler.\nAC:L - The attacker can create both conflicting file handles, obtain the deferred request's AsyncId, and control the CLOSE/CANCEL sequencing, so both sides of the race are attacker-controlled.\nPR:L - SMB2 LOCK requires a valid SMB session, tree connection, and session-owned open file handle. Any ordinary authenticated share user suffices; administrative privileges are unnecessary.\nUI:N - The attacker can create the handles, conflicting locks, and cancellation requests without any victim action.\nS:U - The UAF occurs within the host kernel's ksmbd security authority and does not inherently cross a separate virtualization or sandbox boundary.\nC:H - The file_lock UAF permits attacker-influenced slab reuse and stale kernel-pointer dereferences, making kernel memory disclosure defensible.\nI:H - The stale callback performs list deletion and wait-queue operations through freed or reallocated fields, enabling kernel heap corruption, arbitrary-write primitives, and potential code execution.\nA:H - The UAF reaches __locks_delete_block or __wake_up_common and can cause a kernel oops or panic; a remote attacker can repeatedly retrigger it."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/server/smb2pdu.c"], "versions": [{"version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "367c42a611fe488b7b03f1f6737f4dee0e8b20a2", "status": "affected", "versionType": "git"}, {"version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "7703fd9aba1f2483c8e55f9ff73b7663e0761ed9", "status": "affected", "versionType": "git"}, {"version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "463bbd79698513af4dad50fe1c573825f297ca2e", "status": "affected", "versionType": "git"}, {"version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "5aa1cb01155f96824003baf7997cdf1f150caba3", "status": "affected", "versionType": "git"}, {"version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "5c75275c0fc9a2deb0d8f5604edcb16f288171c8", "status": "affected", "versionType": "git"}, {"version": "e2f34481b24db2fd634b5edb0a5bd0e4d38cc6e9", "lessThan": "d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e", "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/smb2pdu.c"], "versions": [{"version": "5.15", "status": "affected"}, {"version": "0", "lessThan": "5.15", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.178", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.145", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.96", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.18.39", "lessThanOrEqual": "6.18.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.1.4", "lessThanOrEqual": "7.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "7.2", "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": "6.1.178"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.6.145"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.12.96"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.18.39"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "7.1.4"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "7.2"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/367c42a611fe488b7b03f1f6737f4dee0e8b20a2"}, {"url": "https://git.kernel.org/stable/c/7703fd9aba1f2483c8e55f9ff73b7663e0761ed9"}, {"url": "https://git.kernel.org/stable/c/463bbd79698513af4dad50fe1c573825f297ca2e"}, {"url": "https://git.kernel.org/stable/c/5aa1cb01155f96824003baf7997cdf1f150caba3"}, {"url": "https://git.kernel.org/stable/c/5c75275c0fc9a2deb0d8f5604edcb16f288171c8"}, {"url": "https://git.kernel.org/stable/c/d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e"}], "title": "ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation", "x_generator": {"engine": "bippy-1.2.0"}}}}

{}

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The cancel\ncallback smb2_remove_blocked_lock() holds a reference to the flock.\n\nIf the lock waiter is subsequently woken up but the work state is no\nlonger KSMBD_WORK_ACTIVE (e.g., due to a concurrent cancellation), the\ncleanup path calls locks_free_lock(flock) without dequeuing the work from\nthe async_requests list. Concurrently, smb2_cancel() walks the list\nunder conn->request_lock and invokes the cancel callback, which then\ndereferences the already freed 'flock'. This leads to a slab-use-after-free\ninside __wake_up_common.\n\nFix this by restructuring the cleanup logic after the worker returns\nfrom ksmbd_vfs_posix_lock_wait(). Move list_del(&smb_lock->llist) and\nrelease_async_work(work) to the top of the cleanup block. This guarantees\nthat the async work is completely dequeued and serialized under\nconn->request_lock before locks_free_lock(flock) is called, rendering\nthe flock unreachable for any concurrent smb2_cancel()."}], "id": "CVE-2026-64396", "lastModified": "2026-09-04T14:47:23.990", "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"}]}, "published": "2026-07-25T10:17:23.040", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/367c42a611fe488b7b03f1f6737f4dee0e8b20a2"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/463bbd79698513af4dad50fe1c573825f297ca2e"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/5aa1cb01155f96824003baf7997cdf1f150caba3"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/5c75275c0fc9a2deb0d8f5604edcb16f288171c8"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/7703fd9aba1f2483c8e55f9ff73b7663e0761ed9"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d20d1c8ba5765d1d12eefc0aee6385ab3f240e1e"}], "sourceIdentifier": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-416"}], "source": "nvd@nist.gov", "type": "Primary"}]}

{"bugzilla": {"description": "kernel: ksmbd: fix UAF of struct file_lock in SMB2_LOCK deferred-lock cancellation", "id": "2507037", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2507037"}, "csaw": false, "cwe": "CWE-825", "details": ["No description is available for this CVE."], "name": "CVE-2026-64396", "package_state": [{"cpe": "cpe:/a:redhat:hummingbird:1", "fix_state": "Not affected", "impact": "important", "package_name": "erlang27", "product_name": "Red Hat Hardened Images"}], "public_date": "2026-07-25T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-64396\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-64396\nhttps://lore.kernel.org/linux-cve-announce/2026072528-CVE-2026-64396-7ca2@gregkh/T"]}

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