{ "dataType": "CVE_RECORD", "dataVersion": "5.2", "cveMetadata": { "cveId": "CVE-2025-21994", "assignerOrgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "state": "PUBLISHED", "assignerShortName": "Linux", "dateReserved": "2024-12-29T08:45:45.801Z", "datePublished": "2025-04-02T14:00:37.407Z", "dateUpdated": "2026-08-05T11:55:53.957Z" }, "containers": { "cna": { "providerMetadata": { "orgId": "416baaa9-dc9f-4396-8d5f-8c081fb06d67", "shortName": "Linux", "dateUpdated": "2026-08-05T11:55:53.957Z" }, "descriptions": [ { "lang": "en", "value": "In the Linux kernel, the following vulnerability has been resolved:\n\nksmbd: fix incorrect validation for num_aces field of smb_acl\n\nparse_dcal() validate num_aces to allocate posix_ace_state_array.\n\nif (num_aces > ULONG_MAX / sizeof(struct smb_ace *))\n\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." } ], "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 — 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 × ~4 MB `posix_ace_state_array` plus ~2.8 MB `ppace`), a ~200,000× amplification, and ksmbd's 256-slot `ksmbd-io` workqueue lets a few connections drive gigabytes of concurrent order-8/order-10 allocation pressure — 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" } } ] } }