CVE-2026-52921 netfilter: ipset: stop hash:* range iteration at end
A flaw in Linux kernel netfilter ipset allows infinite loops during IPv4 range iteration, potentially causing denial of service.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-52921?
CVE-2026-52921 is a medium-severity denial of service vulnerability in Linux kernel, published on 24 Jun 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
In the Linux kernel, the following vulnerability has been resolved:
netfilter: ipset: stop hash:* range iteration at end
The following hash set variants:
hash:ip,mark hash:ip,port hash:ip,port,ip hash:ip,port,net
iterate IPv4 ranges with a 32-bit iterator.
The iterator must stop once the last address in the requested range has been processed. Advancing it once more can move the traversal state past the end of the request, so a later retry may continue from an unintended position.
Handle the iterator increment explicitly at the end of the loop and stop once the upper bound has been processed. This keeps the existing retry behaviour intact for valid ranges while preventing traversal from continuing past the original boundary.
Weakness: CWE-835
Which versions are affected by CVE-2026-52921?
It affects 1 product.
Products include Linux kernel.
How do I fix CVE-2026-52921?
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-2026-52921 being exploited?
There is no known exploitation of CVE-2026-52921 in the wild and no public exploit code.
Other vulnerabilities in Linux kernel
Sources
Also known as AZL-90549, BELL-CVE-2026-52921, DEBIAN-CVE-2026-52921, GHSA-3v47-mwg3-xvq2, ROOT-OS-UBUNTU-2204-CVE-2026-52921, ROOT-OS-UBUNTU-2404-CVE-2026-52921 and 1 more.