CVE-2026-80586 mptcp: options: reset DSS fields in case of unexpected size
A remote peer can cause a denial of service in the Linux kernel by sending malformed MPTCP DSS options that leave fields uninitialized.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80586?
CVE-2026-80586 is a critical vulnerability in Linux, published on 26 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:
mptcp: options: reset DSS fields in case of unexpected size
A remote peer could send a malformed DSS with a wrong size, followed by another DSS or MPC + Data. In this case, the first suboption will be ignored, but leaving some fields written, which could lead to inconsistency or access uninitialized data.
Explicitly reset the fields that could have been modified in case of unexpected size.
Which versions are affected by CVE-2026-80586?
How do I fix CVE-2026-80586?
Apply the vendor's patch.
Is CVE-2026-80586 being exploited?
There is no known exploitation of CVE-2026-80586 in the wild and no public exploit code.
Sources
Also known as AZL-97776, BELL-CVE-2026-80586, DEBIAN-CVE-2026-80586, GHSA-6f65-mfmh-h759, UBUNTU-CVE-2026-80586.