Vulnerability Description
Mailpit is an email testing tool and API for developers. Prior to 1.30.2, the remediation shipped for CVE-2026-27808 is incomplete because the tools.IsInternalIP deny-list in internal/tools/net.go relies on Go's standard library classification helpers and does not block IPv6 transition mechanisms or prefixes such as NAT64, 6to4, IPv4-compatible IPv6, ISATAP, fec0::/10, and 2001:db8::/32. An attacker who can deliver email and invoke POST /api/v1/message/{ID}/link-check can coerce the Link Check API's safeDialContext path into dialing internal destinations and can use status-code and error feedback to map internal service reachability, including cloud metadata endpoints. This issue is fixed in version 1.30.2.
CVSS Score
MEDIUM
Related Weaknesses (CWE)
References
- https://github.com/axllent/mailpit/commit/a88dadbbe1df016a35a445089ef2a362a6c2de
- https://github.com/axllent/mailpit/releases/tag/v1.30.2
- https://github.com/axllent/mailpit/security/advisories/GHSA-w4mc-hhc6-xp28
- https://github.com/axllent/mailpit/security/advisories/GHSA-w4mc-hhc6-xp28
FAQ
What is CVE-2026-55187?
CVE-2026-55187 is a vulnerability with a CVSS score of 5.8 (MEDIUM). Mailpit is an email testing tool and API for developers. Prior to 1.30.2, the remediation shipped for CVE-2026-27808 is incomplete because the tools.IsInternalIP deny-list in internal/tools/net.go rel...
How severe is CVE-2026-55187?
CVE-2026-55187 has been rated MEDIUM with a CVSS base score of 5.8/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-55187?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.