CVE-2025-21994

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Use this to check invalid num_aces."}], "metrics": [{"cvssV3_1": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H", "baseScore": 7.6, "baseSeverity": "HIGH"}, "scenarios": [{"lang": "en", "value": "AV:N - ksmbd is the in-kernel SMB server listening on TCP/445, and the malformed `num_aces`/DACL arrives directly in an SMB2_SET_INFO (SMB2_O_INFO_SECURITY) or SMB2_CREATE SD_BUFFER request payload. No local access to the target is needed at any point.\nAC:L - The attacker simply sets the 16/32-bit `num_aces` field of the DACL header to a large value while keeping `pdacl->size` minimal; the oversized allocations follow deterministically on the first request with no race, no memory-layout dependency, and no non-default configuration beyond ksmbd being enabled.\nPR:L - `smb2_set_info()` is reached only after SMB2 session setup, and it additionally requires `KSMBD_TREE_CONN_FLAG_WRITABLE` on the tree connect plus a valid file handle, so any ordinary share account (or the guest account where the share permits it) suffices \u2014 but unauthenticated access does not.\nUI:N - The attacker completes the session setup, tree connect, open and SET_INFO sequence entirely on its own. No administrator or client-side victim action is involved.\nS:U - The oversized allocations and the misparsed ACL stay entirely within the kernel's own security authority on the SMB server host; no VM, IOMMU, container, or sandbox boundary is crossed.\nC:L - The same commit removes a `sid.sub_auth[num_subauth - 1]` negative-index read that, with `num_subauth == 0`, reads the four bytes preceding `sub_auth` and feeds them to `sid_to_id()` and the group-SID test. The read is strictly bounded to 4 bytes that lie inside the client's own request buffer (`end_of_acl` is validated by `ksmbd_smb2_check_message()`), so it is a limited misread rather than an arbitrary kernel-memory disclosure.\nI:L - `parse_dacl()`'s output is applied to the file through `set_posix_acl()` and `notify_change()` in `set_info_sec()`, so an ACL parsed from an unvalidated ACE count and an out-of-bounds `sub_auth[-1]` value yields on-disk permissions and uid/gid mappings that do not correspond to the descriptor sent. This is bounded metadata corruption on files the attacker can already write; the `num_aces`-sized `ppace` and `posix_ace_state_array` writes remain in bounds and the `init_acl_state()` `int` truncation is unreachable because the paired `kmalloc_array()` fails first, so there is no arbitrary-write primitive.\nA:H - A ~120-byte request forces up to ~19 MB of high-order `GFP_KERNEL` allocations (4 \u00d7 ~4 MB `posix_ace_state_array` plus ~2.8 MB `ppace`), a ~200,000\u00d7 amplification, and ksmbd's 256-slot `ksmbd-io` workqueue lets a few connections drive gigabytes of concurrent order-8/order-10 allocation pressure \u2014 producing direct-reclaim/compaction stalls, page-allocation-failure splats (fatal under `panic_on_warn`), and OOM kills that take down the host, which is especially severe on the NAS, router, and embedded devices where ksmbd is commonly deployed."}]}], "affected": [{"product": "Linux", "vendor": "Linux", "defaultStatus": "unaffected", "repo": "https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git", "programFiles": ["fs/smb/server/smbacl.c"], "versions": [{"version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "lessThan": "c3a3484d9d31b27a3db0fab91fcf191132d65236", "status": "affected", "versionType": "git"}, {"version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "lessThan": "9c4e202abff45f8eac17989e549fc7a75095f675", "status": "affected", "versionType": "git"}, {"version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "lessThan": "d0f87370622a853b57e851f7d5a5452b72300f19", "status": "affected", "versionType": "git"}, {"version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "lessThan": "a4cb17797a5d241f1e509cb5b46ed95a80c2f5fd", "status": "affected", "versionType": "git"}, {"version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "lessThan": "f6a6721802ac2f12f4c1bbe839a4c229b61866f2", "status": "affected", "versionType": "git"}, {"version": "0626e6641f6b467447c81dd7678a69c66f7746cf", "lessThan": "1b8b67f3c5e5169535e26efedd3e422172e2db64", "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/smbacl.c"], "versions": [{"version": "5.15", "status": "affected"}, {"version": "0", "lessThan": "5.15", "status": "unaffected", "versionType": "semver"}, {"version": "5.15.180", "lessThanOrEqual": "5.15.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.1.132", "lessThanOrEqual": "6.1.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.6.85", "lessThanOrEqual": "6.6.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.12.21", "lessThanOrEqual": "6.12.*", "status": "unaffected", "versionType": "semver"}, {"version": "6.13.9", "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": "5.15.180"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.1.132"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.6.85"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.12.21"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.13.9"}, {"vulnerable": true, "criteria": "cpe:2.3:o:linux:linux_kernel:*:*:*:*:*:*:*:*", "versionStartIncluding": "5.15", "versionEndExcluding": "6.14"}]}]}], "references": [{"url": "https://git.kernel.org/stable/c/c3a3484d9d31b27a3db0fab91fcf191132d65236"}, {"url": "https://git.kernel.org/stable/c/9c4e202abff45f8eac17989e549fc7a75095f675"}, {"url": "https://git.kernel.org/stable/c/d0f87370622a853b57e851f7d5a5452b72300f19"}, {"url": "https://git.kernel.org/stable/c/a4cb17797a5d241f1e509cb5b46ed95a80c2f5fd"}, {"url": "https://git.kernel.org/stable/c/f6a6721802ac2f12f4c1bbe839a4c229b61866f2"}, {"url": "https://git.kernel.org/stable/c/1b8b67f3c5e5169535e26efedd3e422172e2db64"}], "title": "ksmbd: fix incorrect validation for num_aces field of smb_acl", "x_generator": {"engine": "bippy-1.2.0"}}, "adp": [{"title": "CVE Program Container", "references": [{"url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"}], "providerMetadata": {"orgId": "af854a3a-2127-422b-91ae-364da2661108", "shortName": "CVE", "dateUpdated": "2025-11-03T19:40:35.107Z"}}]}}

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Use this to check invalid num_aces."}, {"lang": "es", "value": "En el kernel de Linux, se ha resuelto la siguiente vulnerabilidad: ksmbd: Se corrige la validaci\u00f3n incorrecta del campo num_aces de smb_acl. La funci\u00f3n parse_dcal() valida num_aces para asignar posix_ace_state_array. Si (num_aces > ULONG_MAX / sizeof(struct smb_ace *)), se considera una validaci\u00f3n incorrecta que permita crear una matriz de tama\u00f1o ULONG_MAX. smb_acl tiene el campo ->size para calcular el n\u00famero real de ases en el tama\u00f1o del b\u00fafer de solicitud. \u00daselo para comprobar num_aces no v\u00e1lidos."}], "id": "CVE-2025-21994", "lastModified": "2026-07-30T06:22:02.047", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.6, "baseSeverity": "HIGH", "confidentialityImpact": "LOW", "integrityImpact": "LOW", "privilegesRequired": "LOW", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H", "version": "3.1"}, "exploitabilityScore": 2.8, "impactScore": 4.7, "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": "2025-04-02T14:16:01.440", "references": [{"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/1b8b67f3c5e5169535e26efedd3e422172e2db64"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/9c4e202abff45f8eac17989e549fc7a75095f675"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/a4cb17797a5d241f1e509cb5b46ed95a80c2f5fd"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/c3a3484d9d31b27a3db0fab91fcf191132d65236"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/d0f87370622a853b57e851f7d5a5452b72300f19"}, {"source": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "tags": ["Patch"], "url": "https://git.kernel.org/stable/c/f6a6721802ac2f12f4c1bbe839a4c229b61866f2"}, {"source": "af854a3a-2127-422b-91ae-364da2661108", "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"}], "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: fix incorrect validation for num_aces field of smb_acl", "id": "2356924", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2356924"}, "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"}, "cwe": "CWE-99", "details": ["In the Linux kernel, the following vulnerability has been resolved:\nksmbd: fix incorrect validation for num_aces field of smb_acl\nparse_dcal() validate num_aces to allocate posix_ace_state_array.\nif (num_aces > ULONG_MAX / sizeof(struct smb_ace *))\nIt is an incorrect validation that we can create an array of size ULONG_MAX.\nsmb_acl has ->size field to calculate actual number of aces in request buffer\nsize. Use this to check invalid num_aces."], "name": "CVE-2025-21994", "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": "2025-04-02T00:00:00Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2025-21994\nhttps://nvd.nist.gov/vuln/detail/CVE-2025-21994\nhttps://lore.kernel.org/linux-cve-announce/2025040214-CVE-2025-21994-44bf@gregkh/T"], "threat_severity": "Moderate"}

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