CVE-2025-39764: linux kernel — Fix

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: remove refcounting in expectation dumpers Same pattern as previous patch: do not keep the expectation object alive via refcount, only store a cookie value and then use that as the skip hint for dump resumption. AFAICS this has the same issue as the one resolved in the conntrack dumper, when we do if (!refcount_inc_not_zero(&exp->use)) to increment the refcount, there is a chance that exp == last, which causes a double-increment of the refcount and subsequent memory leak.

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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

Affected Products

Vendor	Product	Versions
linux	linux_kernel	2.6.23 — 6.16.2
linux	linux_kernel	All

References

Advisories & Patches

https://git.kernel.org/stable/c/1492e3dcb2be3aa46d1963da96aa9593e4e4db5a https://git.kernel.org/stable/c/a4d634ded4d3d400f115d84f654f316f249531c9

Other References

https://git.kernel.org/stable/c/078d33c95bf534d37aa04269d1ae6158e20082d5 https://git.kernel.org/stable/c/64b7684042246e3238464c66894e30ba30c7e851 https://git.kernel.org/stable/c/9e5021a906532ca16e2aac69c0607711e1c70b1f https://git.kernel.org/stable/c/b05500444b8eb97644efdd180839a04a706be97c https://git.kernel.org/stable/c/bada48ad5b0590e318d0f79636ff62a2ef9f4955

Frequently Asked Questions

What is CVE-2025-39764? +

In the Linux kernel, the following vulnerability has been resolved: netfilter: ctnetlink: remove refcounting in expectation dumpers Same pattern as previous patch: do not keep the expectation object alive via refcount, only store a cookie value and then use that as the skip hint for dump resumption. AFAICS this has the same issue as the one resolved in the conntrack dumper, when we do if (!refcount_inc_not_zero(&exp->use)) to increment the refcount, there is a chance that exp == last, which causes a double-increment of the refcount and subsequent memory leak. It has a CVSS v3.1 base score of 5.5 (MEDIUM).

How severe is CVE-2025-39764? +

CVE-2025-39764 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-2025-39764? +

CVE-2025-39764 affects products from linux, specifically: linux_kernel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2025-39764? +

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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