CVE-2026-80586: mptcp: options: reset DSS fields in case of unexpected size
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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Upgrade
Upgrade to a fixed release to a version that resolves this vulnerability.
Fixed in 6.6.157.1-1
Event History
Frequently Asked Questions
Who can trigger the flaw?
A remote peer that can send MPTCP traffic to the affected Linux kernel can trigger it by supplying malformed DSS option data followed by another DSS option or MPC plus Data.
What condition makes the malformed input problematic?
The issue occurs when a DSS suboption has an unexpected size. Although that suboption is ignored, fields it modified may remain set and affect parsing of subsequent DSS or MPC plus Data options.
What is the practical impact described for affected systems?
The stale DSS fields can create inconsistent state or lead to access to uninitialized data.
What mitigation is described when applying the fix?
The described fix explicitly resets DSS fields that may have been modified when a DSS option has an unexpected size. The provided references identify stable Linux kernel commits containing that correction.