Vulnerability-Lookup

GHSA-PCV3-R2V8-4964

Vulnerability from github – Published: 2025-04-02 15:31 – Updated: 2025-11-03 21:33

Details

In the Linux kernel, the following vulnerability has been resolved:

ksmbd: fix incorrect validation for num_aces field of smb_acl

parse_dcal() validate num_aces to allocate posix_ace_state_array.

if (num_aces > ULONG_MAX / sizeof(struct smb_ace *))

It is an incorrect validation that we can create an array of size ULONG_MAX. smb_acl has ->size field to calculate actual number of aces in request buffer size. Use this to check invalid num_aces.

Severity

5.5 (Medium)


                  
                    CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

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{
  "affected": [],
  "aliases": [
    "CVE-2025-21994"
  ],
  "database_specific": {
    "cwe_ids": [],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2025-04-02T14:16:01Z",
    "severity": "MODERATE"
  },
  "details": "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 \u003e 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 -\u003esize field to calculate actual number of aces in request buffer\nsize. Use this to check invalid num_aces.",
  "id": "GHSA-pcv3-r2v8-4964",
  "modified": "2025-11-03T21:33:29Z",
  "published": "2025-04-02T15:31:37Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2025-21994"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/1b8b67f3c5e5169535e26efedd3e422172e2db64"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/9c4e202abff45f8eac17989e549fc7a75095f675"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/a4cb17797a5d241f1e509cb5b46ed95a80c2f5fd"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/c3a3484d9d31b27a3db0fab91fcf191132d65236"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/d0f87370622a853b57e851f7d5a5452b72300f19"
    },
    {
      "type": "WEB",
      "url": "https://git.kernel.org/stable/c/f6a6721802ac2f12f4c1bbe839a4c229b61866f2"
    },
    {
      "type": "WEB",
      "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

CVE-2025-21994 (GCVE-0-2025-21994)

Vulnerability from cvelistv5 – Published: 2025-04-02 14:00 – Updated: 2026-08-05 11:55

Title

ksmbd: fix incorrect validation for num_aces field of smb_acl

Summary

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix incorrect validation for num_aces field of smb_acl parse_dcal() validate num_aces to allocate posix_ace_state_array. if (num_aces > ULONG_MAX / sizeof(struct smb_ace *)) It is an incorrect validation that we can create an array of size ULONG_MAX. smb_acl has ->size field to calculate actual number of aces in request buffer size. Use this to check invalid num_aces.

Severity

7.6 (High)


                        
                          CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H

Assigner

Linux mitre root

References

7 references

URL	Tags
https://git.kernel.org/stable/c/c3a3484d9d31b27a3…
https://git.kernel.org/stable/c/9c4e202abff45f8ea…
https://git.kernel.org/stable/c/d0f87370622a853b5…
https://git.kernel.org/stable/c/a4cb17797a5d241f1…
https://git.kernel.org/stable/c/f6a6721802ac2f12f…
https://git.kernel.org/stable/c/1b8b67f3c5e516953…
https://lists.debian.org/debian-lts-announce/2025…

Impacted products

2 products

Vendor	Product	Version
Linux	Linux	Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < c3a3484d9d31b27a3db0fab91fcf191132d65236 (git) Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < 9c4e202abff45f8eac17989e549fc7a75095f675 (git) Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < d0f87370622a853b57e851f7d5a5452b72300f19 (git) Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < a4cb17797a5d241f1e509cb5b46ed95a80c2f5fd (git) Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < f6a6721802ac2f12f4c1bbe839a4c229b61866f2 (git) Affected: 0626e6641f6b467447c81dd7678a69c66f7746cf , < 1b8b67f3c5e5169535e26efedd3e422172e2db64 (git)
Linux	Linux	Affected: 5.15 Unaffected: 0 , < 5.15 (semver) Unaffected: 5.15.180 , ≤ 5.15.* (semver) Unaffected: 6.1.132 , ≤ 6.1.* (semver) Unaffected: 6.6.85 , ≤ 6.6.* (semver) Unaffected: 6.12.21 , ≤ 6.12.* (semver) Unaffected: 6.13.9 , ≤ 6.13.* (semver) Unaffected: 6.14 , ≤ * (original_commit_for_fix)

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JSON

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    "adp": [
      {
        "providerMetadata": {
          "dateUpdated": "2025-11-03T19:40:35.107Z",
          "orgId": "af854a3a-2127-422b-91ae-364da2661108",
          "shortName": "CVE"
        },
        "references": [
          {
            "url": "https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html"
          }
        ],
        "title": "CVE Program Container"
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          "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 \u003e 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 -\u003esize field to calculate actual number of aces in request buffer\nsize. Use this to check invalid num_aces."
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              "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-\u003esize` 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\u0027s 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\u0027s 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()`\u0027s 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\u0027s 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."
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    "dateUpdated": "2026-08-05T11:55:53.957Z",
    "state": "PUBLISHED"
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Sightings

Author	Source	Type	Date	Other

Nomenclature

Seen: The vulnerability was mentioned, discussed, or observed by the user.
Confirmed: The vulnerability has been validated from an analyst's perspective.
Published Proof of Concept: A public proof of concept is available for this vulnerability.
Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
Not confirmed: The user expressed doubt about the validity of the vulnerability.
Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.

Detection rules are retrieved from Rulezet.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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