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CVE-2025-37899: ksmbd: fix use-after-free in session logoff

• Severity: high (CVSS 7.8 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2025-05-20 · updated 2026-07-30
• Weakness: CWE-416

Description

In the Linux kernel, the following vulnerability has been resolved: ksmbd: fix use-after-free in session logoff The sess->user object can currently be in use by another thread, for example if another connection has sent a session setup request to bind to the session being free'd. The handler for that connection could be in the smb2_sess_setup function which makes use of sess->user.

Affected products

• Linux kernel: from 5.15 before 6.12.28; from 6.13 before 6.14.6; 6.15-rc1, 6.15-rc2, 6.15-rc3, 6.15-rc4 — fixed in 6.12.28, 6.14.6

How to fix

Upgrade to a fixed version: Linux kernel 6.12.28, 6.14.6. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/02d16046cd11a5c037b28c12ffb818c56dd3ef43
• https://git.kernel.org/stable/c/2fc9feff45d92a92cd5f96487655d5be23fb7e2b
• https://git.kernel.org/stable/c/70ad6455139e26e85f48f95d0e21f351c1909342
• https://git.kernel.org/stable/c/931dc8a3670f71c45c0b1379ea4e92dafbda1aca
• https://git.kernel.org/stable/c/d5ec1d79509b3ee01de02c236f096bc050221b7f
• https://news.ycombinator.com/item?id=44081338
• https://sean.heelan.io/2025/05/22/how-i-used-o3-to-find-cve-2025-37899-a-remote-zeroday-vulnerability-in-the-linux-kernels-smb-implementation/

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