CVE-2026-80637 netfilter: synproxy: fix unaligned memory access in timestamp adjustment
An attacker can cause a kernel crash or performance degradation on strict alignment architectures by triggering unaligned memory access in the netfilter synproxy module.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80637?
CVE-2026-80637 is a high-severity denial of service vulnerability in Linux, published on 28 Aug 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: synproxy: fix unaligned memory access in timestamp adjustment
Use get_unaligned_be32() and put_unaligned_be32() to safely read and write the timestamp fields. This prevents performance degradation due to unaligned memory access or even a crash on strict alignment architectures.
This follows the implementation of timestamp parsing in the networking stack at tcp_parse_options() and synproxy_parse_options().
Which versions are affected by CVE-2026-80637?
How do I fix CVE-2026-80637?
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-2026-80637 being exploited?
There is no known exploitation of CVE-2026-80637 in the wild and no public exploit code.
Sources
Also known as AZL-98132, BELL-CVE-2026-80637, DEBIAN-CVE-2026-80637, GHSA-h35g-h9xw-jfv9, UBUNTU-CVE-2026-80637.