CVE-2026-80586
Received Received - Intake

MPTCP DSS Field Reset in Linux Kernel

Publication date: 2026-08-26

Last updated on: 2026-08-26

Assigner: kernel.org

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.

CVSS Scores

EPSS Scores

Probability:
Percentile:

Meta Information

Published
2026-08-26
Last Modified
2026-08-26
Generated
2026-08-26
AI Q&A
2026-08-26
EPSS Evaluated
N/A
NVD
CVE-2026-80586
EUVD
EUVD-2026-66501

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
linux linux_kernel *

Helpful Resources

Exploitability

CWE
CWE Icon
KEV
KEV Icon
CWE ID Description
CWE-UNKNOWN

Attack-Flow Graph

AI Quick Actions

Instant insights powered by AI
Executive Summary

This vulnerability in the Linux kernel involves a remote peer sending a malformed DSS (Data Sequence Signal) with an incorrect size. This can cause the first suboption to be ignored while leaving some fields written, leading to inconsistency or access to uninitialized data in the kernel.

Detection Guidance

This vulnerability involves malformed DSS options in MPTCP connections. Detection requires monitoring for unexpected MPTCP suboptions or malformed packets. Use tcpdump to capture MPTCP traffic and analyze for malformed DSS fields. Example command: tcpdump -i any -s 0 -w mptcp_capture.pcap 'tcp port 1024 and ((tcp[12:1] & 0xf0) >> 2) >= 20 and (tcp[((tcp[12:1] & 0xf0) >> 2)+9] & 0x80) == 0x80'

Inspect kernel logs for MPTCP-related errors or warnings. Check for inconsistent DSS fields in captured packets. Tools like Wireshark can help analyze MPTCP traffic for malformed suboptions.

Impact Analysis

This vulnerability could allow an attacker to cause system instability, crashes, or unexpected behavior by exploiting the inconsistency in DSS fields. It may also lead to unauthorized data access or corruption if uninitialized memory is read.

Mitigation Strategies

Update the Linux kernel to the latest stable version that includes the fix for this vulnerability. Disable MPTCP if not required by your use case. Apply network-level mitigations like firewalls to filter malformed MPTCP packets.

Monitor network traffic for signs of exploitation attempts. Ensure intrusion detection systems are updated to detect MPTCP-related anomalies.

Chat Assistant

Ask questions about this CVE
Hi! I’m here to help you understand CVE-2026-80586. Ask me anything about the vulnerability, its impact, or mitigation strategies.
0/70

EPSS Chart