CVE-2025-39838: cifs: prevent NULL pointer dereference in UTF16 conversion

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: 2025-09-19 · updated 2026-10-19
Weakness: CWE-476

Description

In the Linux kernel, the following vulnerability has been resolved: cifs: prevent NULL pointer dereference in UTF16 conversion There can be a NULL pointer dereference bug here. NULL is passed to __cifs_sfu_make_node without checks, which passes it unchecked to cifs_strndup_to_utf16, which in turn passes it to cifs_local_to_utf16_bytes where '*from' is dereferenced, causing a crash. This patch adds a check for NULL 'src' in cifs_strndup_to_utf16 and returns NULL early to prevent dereferencing NULL pointer. Found by Linux Verification Center (linuxtesting.org) with SVACE

Affected products

Debian Linux: 11.0
Linux kernel: from 6.12 before 6.12.46; from 6.13 before 6.16.6; 6.17-rc1, 6.17-rc2, 6.17-rc3, 6.17-rc4 — fixed in 6.12.46, 6.16.6

How to fix

Upgrade to a fixed version: Linux kernel 6.12.46, 6.16.6. Check the vendor advisory for mitigations.

References

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