What’s Vulnerable › Vulnerabilities

CVE-2026-23139: netfilter: nf_conncount: update last_gc only when GC has been performed

• Severity: medium (CVSS 5.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-02-14 · updated 2026-06-17

Description

In the Linux kernel, the following vulnerability has been resolved: netfilter: nf_conncount: update last_gc only when GC has been performed Currently last_gc is being updated everytime a new connection is tracked, that means that it is updated even if a GC wasn't performed. With a sufficiently high packet rate, it is possible to always bypass the GC, causing the list to grow infinitely. Update the last_gc value only when a GC has been actually performed.

Affected products

• Linux kernel: from 5.19 before 6.1.161; from 6.2 before 6.6.121; from 6.7 before 6.12.66; from 6.13 before 6.18.6; 6.19-rc1, 6.19-rc2, 6.19-rc3, 6.19-rc4 — fixed in 6.1.161, 6.12.66, 6.18.6, 6.6.121

How to fix

Upgrade to a fixed version: Linux kernel 6.1.161, 6.12.66, 6.18.6, 6.6.121. Check the vendor advisory for mitigations.

References

• https://git.kernel.org/stable/c/26a82dce2beee39c43c109d9647e16f49cb02a35
• https://git.kernel.org/stable/c/2c7c71113ed6d3e2f3aca4c088f22283016ff34f
• https://git.kernel.org/stable/c/3cd717359e56f82f06cbf8279b47a7d79880c6f3
• https://git.kernel.org/stable/c/7811ba452402d58628e68faedf38745b3d485e3c
• https://git.kernel.org/stable/c/8bdafdf4900040a81422056cabe5e00a37bd101a
• https://git.kernel.org/stable/c/9f45588993d7f115280fc726119ca86fba32a811
• https://git.kernel.org/stable/c/c4cde57c8affdcca5bcff53a1047e15d268bdca1

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