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Review reviewHigh

CVE-2026-42504

Go standard library mime

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

CVSS
7.5
EPSS
0.56%
43.4% percentile
CISA KEV
Not listed
Published
2026.06.03
PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV
Exploit probability0.56%
Technical severityCVSS 7.5

Vulnerability overview

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

Affected product and versions

Product
Go standard library mime
Affected versions
< 1.25.11, >= 1.26.0-0 < 1.26.4
Fixed versions
No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide
  1. 1
    Identify

    Confirm that Go standard library mime and an affected version are present.

  2. 2
    Prioritize

    Combine exploitation signals with asset exposure and business criticality.

  3. 3
    Remediate

    Follow the vendor advisory or supported update path and preserve rollback options.

  4. 4
    Verify

    Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE
CWE-407