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CVE-2025-21944: ksmbd: fix bug on trap in smb2_lock

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.2% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2025-04-01 · updated 2026-06-17
• Weakness: CWE-667

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix bug on trap in smb2_lock If lock count is greater than 1, flags could be old value. It should be checked with flags of smb_lock, not flags. It will cause bug-on trap from locks_free_lock in error handling routine.

Affected products

• Linux kernel: from 5.15 before 6.1.131; from 6.2 before 6.6.83; from 6.7 before 6.12.19; from 6.13 before 6.13.7; 6.14-rc1, 6.14-rc2, 6.14-rc3, 6.14-rc4, 6.14-rc5 — fixed in 6.1.131, 6.12.19, 6.13.7, 6.6.83

How to fix

Upgrade to a fixed version: Linux kernel 6.1.131, 6.12.19, 6.13.7, 6.6.83. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/11e0e74e14f1832a95092f2c98ed3b99f57797ee
• https://git.kernel.org/stable/c/2b70e3ac79eacbdf32571f7af48dd81cdd957ca8
• https://git.kernel.org/stable/c/8994f0ce8259f812b4f4a681d8298c6ff682efaa
• https://git.kernel.org/stable/c/dbcd7fdd86f77529210fe8978154a81cd479844c
• https://git.kernel.org/stable/c/e26e2d2e15daf1ab33e0135caf2304a0cfa2744b
• https://lists.debian.org/debian-lts-announce/2025/05/msg00045.html

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