CVE-2026-80586

A flaw was found in the Linux kernel's Multipath TCP (mptcp) implementation. A remote attacker could send specially crafted Data Sink Selection (DSS) options with an unexpected size. This could lead to data inconsistency or the access of uninitialized data, potentially resulting in information disclosure or a denial of service.

This vulnerability is rated as Important due to the potential for remote kernel memory corruption and sensitive data disclosure caused by mishandling malformed protocol suboptions over the network. The flaw specifically affects systems handling Multipath TCP traffic, where an attacker communicating across a multipath session can induce inconsistent state parsing. Deployments that do not utilize MPTCP or keep the protocol disabled in kernel networking settings are not exposed to this issue.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

The vulnerability affects the Multipath TCP (MPTCP) feature in the Linux kernel. To mitigate this issue, MPTCP can be disabled by preventing the mptcp kernel module from loading. To disable the mptcp module: 1. Create a new file /etc/modprobe.d/disable-mptcp.conf with the following content: install mptcp /bin/true blacklist mptcp 2. Regenerate the initramfs to ensure the change takes effect on boot: sudo dracut -f -v 3. Reboot the system for the changes to take effect. Disabling MPTCP may impact network performance or functionality for applications that rely on Multipath TCP.