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  4. CVE 2026 42504 quadratic complexity in worddecoderdecodeheader
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Back to active CVEs
High · CVSS 7.5CVE-2026-42504

Quadratic complexity in WordDecoder.DecodeHeader in mimeCVE-2026-42504

Answer in brief

CVE-2026-42504 records a High severity (CVSS 7.5) vulnerability in Quadratic complexity in WordDecoder.DecodeHeader in mime. The current sources do not mark it as known exploited. The current feed maps Go standard library/mime (generic), stdlib (go). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jun 2, 2026Updated Nov 9, 2026Source checked Nov 9, 2026First seen by HOL Aug 10, 2026Material review Nov 9, 2026
Upstream Advisory

Key facts

Risk
High · CVSS 7.5
Exploitation
Not marked as known exploited
Affected software
2 mapped packages or products
Fix availability
Available

Why this deserves its current priority

CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps Go standard library/mime (generic), stdlib (go). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
PackageAffected rangeFixed version
Go standard library/mimegeneric>=0 <1.25.11 || >=1.26.0-0 <1.26.41.25.11, 1.26.4
stdlibgo>=0 <1.25.11 >=1.26.0-0 <1.26.41.25.11, 1.26.4

Recommended response

  1. 1Check inventory. Check lockfiles and deployed manifests for Go standard library/mime, stdlib.
  2. 2Review the reported fix. Update Go standard library/mime to 1.25.11; stdlib to 1.25.11 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

  1. Published upstream

    Jun 2, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  2. Source modified

    Nov 9, 2026

    Evidence: source:cvelist:source_dates:source-dates:record

  3. First seen by HOL

    Aug 10, 2026

Sources and claim methodology

  • Source referencego.dev
  • Source referencego.dev
  • Source referencegroups.google.com
  • Source referencepkg.go.dev
Upstream source description

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

Quoted source text, attributed separately from HOL analysis.

Record context

Vulnerability class
Vulnerability
EPSS
Not reported
CWE IDs
CWE-407
Source
CVE List V5
Source checked
Nov 9, 2026
References
4 linked sources
Open source record