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Vulnerabilities

Vulnerability · CVE-2026-42504

Quadratic complexity in WordDecoder.DecodeHeader in mime

Published Jun 2, 2026 · catalog updated Oct 15, 2026 · Go standard library

Check if you run it

No confirmed exploitation is on record for CVE-2026-42504. EPSS is 0.56%. Act only if a listed version of Go standard library is installed.

Gaps on this record

  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.56%
Remediation
Fix linked
Affected products
Go stdlib · vendor Go standard library mime

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

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • Go stdlib0 → 1.25.11
  • vendor Go standard library mimeversion unspecified

How to fix CVE-2026-42504

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-42504. EPSS is 0.56%. Act only if a listed version of Go standard library is installed.

Which versions are affected?

Compare what you have installed with 0 → 1.25.11. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-407. EPSS 0.56%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Related Odoo Git fixes

Quoted Community commit messages that cite this CVE. Presence of a commit is not proof that every edition or backport includes the fix. Enterprise proprietary diffs are never shown here. Timeline

  • Jun 3, 2026 · referenced

    update to go1.26.4

    update to go1.26.4 This release include 3 security fixes following the security policy: - mime: quadratic complexity in WordDecoder.DecodeHeader Decoding a maliciously-crafted MIME header containing many invalid encoded-words could consume excessive CPU. The MIME decoder now better handles this case. Thanks to p4p3r (https://hackerone.com/p4p3r_hak) for reporting this issue. This is CVE-2026-42504 and Go issue https://go.dev/issue/79217. - net/textproto: arbitrary input are included in errors without any escaping When returning errors, functions in the net/textproto package would include its input as part of the error, without any escaping. Note that said input is often controlled by external parties when using this package naturally. For example, a net/http client uses ReadMIMEHeader when parsing the headers it receive from a server. As a result, an attacker could in…
    https://github.com/moby/moby/commit/c3967c40c0c5c2608ae47bd45e97ebcb76c0bc71

Timeline

Detection, updates, and resolution for this record.

  1. Jun 2, 2026 · Catalog

    Detected

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

  2. Oct 10, 2026 · Catalog

    Fix available

    Go stdlib 0 → 1.25.11

  3. Oct 10, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    stdlib fixed in 1.25.11

  4. Oct 10, 2026 · Catalog

    Updated

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

  5. Oct 15, 2026 · OpenSSF OSV / OSV Scanner

    Fix available

    stdlib fixed in 1.25.11

  6. Oct 15, 2026 · CIRCL Vulnerability Lookup

    Updated

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

  7. Oct 15, 2026 · OpenSSF OSV / OSV Scanner

    Updated

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

Sources

References

Freshness

Last verified in this catalog Oct 18, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.