CVE-2026-42504: Go standard library mime · Inefficient Algorithmic Complexity
Affects Go standard library mimeSource CVE Database V5
Not known to be exploited · CVSS 7.5 High : upgrade to 1.26.4 or 1.25.11 soon.
Data as of 30 Oct 2026, 12:04 UTC
Thin evidence
One scorer or none| CISA-ADP | CVSS 3.1 | 7.5 |
|---|
- EPSS
- 0.5% chance of exploitation in 30 days – higher than 46% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
- CISA SSVC
- Exploitation
- No evidence of active exploitation and no public proof of concept
- Automatable
- Attackers can reliably automate steps 1–4 of the kill chain
- Technical impact
- Limited control over the software or limited information exposure
CISA SSVC assessment, 2026-06-03.
- Patch
- Available – fixed in 1.26.4, 1.25.11
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 2 Jun 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors
A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.
What to do
Upgrade Go standard library mime to 1.26.4 or 1.25.11.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| Go standard librarymime | Affected
| Fixed in
|
| Go standard librarymime | Affected
| Fixed in
|
Gomimepkg:golang/mimeOther threats | Affected
| Fixed in
|
Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.
AI-suggested
Users should upgrade to Go standard library versions 1.25.11 or 1.26.4 or later, where this vulnerability has been fixed. No other mitigation is required as the issue is resolved in these official releases.
Description
Decoding a maliciously-crafted MIME header containing many invalid encoded-words can consume excessive CPU.