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CVE-2025-21994: ksmbd: fix incorrect validation for num_aces field of smb_acl

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-04-02 · updated 2026-07-30

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.

Affected products

• Linux kernel: from 5.15 before 5.15.180; from 5.16 before 6.1.132; from 6.2 before 6.6.85; from 6.7 before 6.12.21; from 6.13 before 6.13.9; 6.14-rc1, 6.14-rc2, 6.14-rc3, 6.14-rc4, 6.14-rc5 — fixed in 5.15.180, 6.1.132, 6.12.21, 6.13.9, 6.6.85

How to fix

Upgrade to a fixed version: Linux kernel 5.15.180, 6.1.132, 6.12.21, 6.13.9. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/1b8b67f3c5e5169535e26efedd3e422172e2db64
• https://git.kernel.org/stable/c/9c4e202abff45f8eac17989e549fc7a75095f675
• https://git.kernel.org/stable/c/a4cb17797a5d241f1e509cb5b46ed95a80c2f5fd
• https://git.kernel.org/stable/c/c3a3484d9d31b27a3db0fab91fcf191132d65236
• https://git.kernel.org/stable/c/d0f87370622a853b57e851f7d5a5452b72300f19
• https://git.kernel.org/stable/c/f6a6721802ac2f12f4c1bbe839a4c229b61866f2
• https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html

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