Quadratic complexity in WordDecoder.DecodeHeader in mime

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Summary

CVECVE-2026-42504
StatePUBLISHED
AssignerGo
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-06-02 23:16:37 UTC
Updated2026-06-03 16:16:30 UTC
DescriptionDecoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.

Risk And Classification

Primary CVSS: v3.1 7.5 HIGH from ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.000180000 probability, percentile 0.047770000 (date 2026-06-03)

Problem Types: CWE-407 | CWE-407: Inefficient Algorithmic Complexity | CWE-407 CWE-407 Inefficient Algorithmic Complexity

VersionSourceTypeScoreSeverityVector
3.1ADPDECLARED7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
3.1134c704f-9b21-4f2e-91b3-4a467353bcc0Secondary7.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Go Standard Library Mime affected 1.25.11 semver Not specified
CNA Go Standard Library Mime affected 1.26.0-0 1.26.4 semver Not specified

References

ReferenceSourceLinkTags
go.dev/cl/774481 [email protected] go.dev
go.dev/issue/79217 [email protected] go.dev
groups.google.com/g/golang-announce/c/tKs3rmcBcKw [email protected] groups.google.com
pkg.go.dev/vuln/GO-2026-5038 [email protected] pkg.go.dev
CVE Program record CVE.ORG www.cve.org canonical
NVD vulnerability detail NVD nvd.nist.gov canonical, analysis

Vendor Comments And Credit

Discovery Credit

CNA: p4p3r (https://hackerone.com/p4p3r_hak) (en)

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