High CPU Overuse via Invalid MIME Header in Go mime before 1.25.11/1.26.4
CVE-2026-42504 Published on June 2, 2026
Quadratic complexity in WordDecoder.DecodeHeader in mime
Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.
Vulnerability Analysis
CVE-2026-42504 is exploitable with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity, and a high impact on availability.
Weakness Type
Inefficient Algorithmic Complexity
An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.
Products Associated with CVE-2026-42504
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Affected Versions
Go standard library mime:- Before 1.25.11 is affected.
- Version 1.26.0-0 and below 1.26.4 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.