{"id":"CVE-2026-55187","aliases":["GHSA-w4mc-hhc6-xp28","GO-2026-5688"],"url":"https://o3.security/vulnerability/CVE-2026-55187","summary":"Mailpit: Incomplete SSRF protection in Link Check API via IPv6 transition mechanisms (follow-up to CVE-2026-27808)","details":"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.","published":"2026-07-10T21:43:59.548Z","modified":"2026-08-12T03:51:45.028344695Z","cvss":{"score":5.8,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N"},"epss":{"score":0.00384,"percentile":0.31909,"asOf":"2026-09-12"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/axllent/mailpit","fixedVersion":"1.30.2"}],"fix":{"url":"https://github.com/axllent/mailpit/commit/a88dadbbe1df016a35a445089ef2a362a6c2de78","label":"axllent/mailpit@a88dadb"},"references":[{"type":"WEB","url":"https://github.com/axllent/mailpit/releases/tag/v1.30.2"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55187.json"},{"type":"ADVISORY","url":"https://github.com/axllent/mailpit/security/advisories/GHSA-w4mc-hhc6-xp28"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55187"},{"type":"FIX","url":"https://github.com/axllent/mailpit/commit/a88dadbbe1df016a35a445089ef2a362a6c2de78"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:45.028344695Z"}}