CVE-2025-39902: debian linux Null Dereference — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: mm/slub: avoid accessing metadata when pointer is invalid in object_err() object_err() reports details of an object for further debugging, such as the freelist pointer, redzone, etc. However, if the pointer is invalid, attempting to access object metadata can lead to a crash since it does not point to a valid object. One known path to the crash is when alloc_consistency_checks() determines the pointer to the allocated object is invalid because of a freelist corruption, and calls object_err() to report it. The debug code should report and handle the corruption gracefully and not crash in the process. In case the pointer is NULL or check_valid_pointer() returns false for the pointer, only print the pointer value and skip accessing metadata.

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CVSS v3.1 Score

5.5

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

Weakness Type (CWE)

CWE-476 CWE-476

Affected Products

Vendor	Product	Versions
linux	linux_kernel	2.6.22 — 5.4.299
linux	linux_kernel	5.5 — 5.10.243
linux	linux_kernel	5.11 — 5.15.192
linux	linux_kernel	5.16 — 6.1.151
linux	linux_kernel	6.2 — 6.6.105
linux	linux_kernel	6.7 — 6.12.46
linux	linux_kernel	6.13 — 6.16.6
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
linux	linux_kernel	All
debian	debian_linux	All

References

Advisories & Patches

https://git.kernel.org/stable/c/0ef7058b4dc6fcef622ac23b45225db57f17b83f https://git.kernel.org/stable/c/1f0797f17927b5cad0fb7eced422f9a7c30a3191 https://git.kernel.org/stable/c/3baa1da473e6e50281324ff1d332d1a07a3bb02e https://git.kernel.org/stable/c/7e287256904ee796c9477e3ec92b07f236481ef3 https://git.kernel.org/stable/c/872f2c34ff232af1e65ad2df86d61163c8ffad42 https://git.kernel.org/stable/c/b4efccec8d06ceb10a7d34d7b1c449c569d53770 https://git.kernel.org/stable/c/dda6ec365ab04067adae40ef17015db447e90736 https://git.kernel.org/stable/c/f66012909e7bf383fcdc5850709ed5716073fdc4

Other References

https://lists.debian.org/debian-lts-announce/2025/10/msg00007.html https://lists.debian.org/debian-lts-announce/2025/10/msg00008.html

Frequently Asked Questions

What is CVE-2025-39902? +

In the Linux kernel, the following vulnerability has been resolved: mm/slub: avoid accessing metadata when pointer is invalid in object_err() object_err() reports details of an object for further debugging, such as the freelist pointer, redzone, etc. However, if the pointer is invalid, attempting to access object metadata can lead to a crash since it does not point to a valid object. One known path to the crash is when alloc_consistency_checks() determines the pointer to the allocated object is invalid because of a freelist corruption, and calls object_err() to report it. The debug code should report and handle the corruption gracefully and not crash in the process. In case the pointer is NULL or check_valid_pointer() returns false for the pointer, only print the pointer value and skip accessing metadata. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-39902? +

CVE-2025-39902 has a CVSS v3.1 score of 5.5 out of 10, rated MEDIUM. This is a medium-severity vulnerability that should be remediated as part of regular maintenance.

What products are affected by CVE-2025-39902? +

CVE-2025-39902 affects products from debian, linux, specifically: debian_linux, linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-39902? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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