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

What is CVE-2026-23139?

CVE-2026-23139 is a high-severity denial of service vulnerability in Linux kernel, published on 14 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official 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.

Which versions are affected by CVE-2026-23139?

It affects 1 product.

Products include Linux kernel.

How do I fix CVE-2026-23139?

Apply the vendor's patch.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2026-23139 being exploited?

There is no known exploitation of CVE-2026-23139 in the wild and no public exploit code.

Other vulnerabilities in Linux kernel

• CVE-2026-53266 Linux Kernel Out-of-Bounds Write Exploited High 8.8
• CVE-2013-6282 Linux Kernel Improper Input Validation Exploited High 8.8
• CVE-2022-0185 Linux Kernel Heap-Based Buffer Overflow Exploited High 8.4
• CVE-2013-2094 Linux Kernel Privilege Escalation Exploited High 8.4
• CVE-2026-53362 Linux Kernel Unspecified Exploited High 7.8

All Linux kernel vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BELL-CVE-2026-23139, DEBIAN-CVE-2026-23139, GHSA-cf2j-m586-269w, ROOT-OS-UBUNTU-2404-CVE-2026-23139, UBUNTU-CVE-2026-23139.