High severity · published Jun 2, 2026
CVE-2026-42504
Quadratic complexity in WordDecoder.DecodeHeader in mime
7.5
CVSS
0.6%
EPSS
No
On KEV
Description
Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 46% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
MI
mime · Go standard library
before 1.25.11; 1.26.0-0 before 1.26.4 · source: vendor