CVE-2026-42504

Quadratic complexity in WordDecoder.DecodeHeader in mime

State: Published
Severity: 7.5 High
Published: Jun 2, 2026
Updated: Nov 2, 2026
Reserved: Apr 28, 2026

Description

Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.

Scores

CVSS	Score	Vector	Source
3.1	7.5 High	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	CISA-ADP

Weaknesses

CWE-407 Inefficient Algorithmic Complexity

Affected Products

Product	Versions
mimeGo standard library	before 1.25.11Affected 1.26.0-0 to before 1.26.4Affected

References

https://go.dev/issue/79217
https://go.dev/cl/774481
https://groups.google.com/g/golang-announce/c/tKs3rmcBcKw
https://pkg.go.dev/vuln/GO-2026-5038

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