TCP MD5 Signature Verification Timing Attack Fix in Linux Kernel

Publication date: 2026-05-08

Last updated on: 2026-06-19

Assigner: kernel.org

Description

In the Linux kernel, the following vulnerability has been resolved: net/tcp-md5: Fix MAC comparison to be constant-time To prevent timing attacks, MACs need to be compared in constant time. Use the appropriate helper function for this.

CVSS Scores

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Meta Information

Published

2026-05-08

Last Modified

2026-06-19

Generated

2026-07-09

AI Q&A

2026-05-08

EPSS Evaluated

2026-07-08

NVD

CVE-2026-43383

EUVD

EUVD-2026-28689

Affected Vendors & Products

Vendor	Product	Version / Range
linux	linux_kernel	7.0
linux	linux_kernel	7.0
linux	linux_kernel	From 6.2 (inc) to 6.6.130 (exc)
linux	linux_kernel	From 6.13 (inc) to 6.18.19 (exc)
linux	linux_kernel	From 6.7 (inc) to 6.12.78 (exc)
linux	linux_kernel	From 6.19 (inc) to 6.19.9 (exc)
linux	linux_kernel	From 5.11 (inc) to 6.1.167 (exc)
linux	linux_kernel	From 2.6.20 (inc) to 5.10.253 (exc)

Helpful Resources

Exploitability

CWE

KEV

CWE ID	Description
CWE-UNKNOWN

Attack-Flow Graph

Executive Summary

This vulnerability is related to the Linux kernel's TCP MD5 implementation. Specifically, the issue was that the Message Authentication Codes (MACs) were not being compared in constant time, which could allow timing attacks. The fix involved using an appropriate helper function to ensure that MAC comparisons are done in constant time, preventing attackers from gaining information based on the time it takes to compare MACs.

Impact Analysis

If the MAC comparison is not done in constant time, an attacker could potentially exploit timing differences to perform a timing attack. This could allow the attacker to deduce the MAC value, compromising the integrity and authenticity of TCP connections that rely on MD5 for security.

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