CVE-2026-45860 netfilter: nf_conncount: increase the connection clean up limit to 64
Attackers can cause connection tracking limits to be reached prematurely, leading to service unavailability in Linux kernel netfilter configurations.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-45860?
CVE-2026-45860 is a high-severity denial of service vulnerability in Linux kernel, published on 27 May 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: increase the connection clean up limit to 64
After the optimization to only perform one GC per jiffy, a new problem was introduced. If more than 8 new connections are tracked per jiffy the list won't be cleaned up fast enough possibly reaching the limit wrongly.
In order to prevent this issue, only skip the GC if it was already triggered during the same jiffy and the increment is lower than the clean up limit. In addition, increase the clean up limit to 64 connections to avoid triggering GC too often and do more effective GCs.
This has been tested using a HTTP server and several performance tools while having nft_connlimit/xt_connlimit or OVS limit configured.
Output of slowhttptest + OVS limit at 52000 connections:
slow HTTP test status on 340th second: initializing: 0 pending: 432 connected: 51998 error: 0 closed: 0 service available: YES
Weakness: CWE-400
Which versions are affected by CVE-2026-45860?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-45860?
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-2026-45860 being exploited?
There is no known exploitation of CVE-2026-45860 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as BELL-CVE-2026-45860, DEBIAN-CVE-2026-45860, GHSA-xwf3-wjqg-p85x, ROOT-OS-DEBIAN-11-CVE-2026-45860, ROOT-OS-UBUNTU-2204-CVE-2026-45860, ROOT-OS-UBUNTU-2404-CVE-2026-45860 and 1 more.