{"id":"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.","aliases":["GHSA-w4mc-hhc6-xp28","GO-2026-5688"],"modified":"2026-08-12T03:51:45.028344695Z","published":"2026-07-10T21:43:59.548Z","related":["openSUSE-SU-2026:21483-1"],"database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-918"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55187.json"},"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"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/axllent/mailpit","events":[{"introduced":"0"},{"fixed":"a88dadbbe1df016a35a445089ef2a362a6c2de78"},{"fixed":"0fb1c79f4bf75418e138424f276f48b4aa4f802b"}],"database_specific":{"source":["AFFECTED_FIELD","REFERENCES"],"extracted_events":[{"introduced":"0"},{"fixed":"1.30.2"}]}}],"versions":["v1.30.1","v1.30.0","v1.29.7","v1.29.6","v1.29.5","v1.29.4","v1.29.3","v1.29.2","v1.29.1","v1.29.0","v1.28.4","v1.28.3","v1.28.2","v1.28.1","v1.28.0","v1.27.11","v1.27.10","v1.27.9","v1.27.8","v1.27.7","v1.27.6","v1.27.5","v1.27.4","v1.27.3","v1.27.2","v1.27.1","v1.27.0","v1.26.2","v1.26.1","v1.26.0","v1.25.1","v1.25.0","v1.24.2","v1.24.1","v1.24.0","v1.23.2","v1.23.1","v1.23.0","v1.22.3","v1.22.2","v1.22.1","v1.22.0","v1.21.8","v1.21.7","v1.21.6","v1.21.5","v1.21.4","v1.21.3","v1.21.2","v1.21.1","v1.21.0","v1.20.7","v1.20.6","v1.20.5","v1.20.4","v1.20.3","v1.20.2","v1.20.1","v1.20.0","v1.19.3","v1.19.2","v1.19.1","v1.19.0","v1.18.7","v1.18.6","v1.18.5","v1.18.4","v1.18.3","v1.18.2","v1.18.1","v1.18.0","v1.17.1","v1.17.0","v1.16.0","v1.15.1","v1.15.0","v1.14.4","v1.14.3","v1.14.2","v1.14.1","v1.14.0","v1.13.3","v1.13.2","v1.13.1","v1.13.0","v1.12.1","v1.12.0","v1.11.1","v1.11.0","v1.10.4","v1.10.3","v1.10.2","v1.10.1","v1.10.0","v1.9.10","v1.9.9","v1.9.8","v1.9.7","v1.9.6","v1.9.5","v1.9.4","v1.9.3","v1.9.2","v1.9.1","v1.9.0","v1.8.4","v1.8.3","v1.8.2","v1.8.1","v1.8.0","v1.7.1","v1.7.0","v1.6.22","v1.6.21","v1.6.20","v1.6.19","v1.6.18","v1.6.17","v1.6.16","v1.6.15","v1.6.14","v1.6.13","v1.6.12","v1.6.11","v1.6.10","v1.6.9","v1.6.8","v1.6.7","v1.6.6","v1.6.5","v1.6.4","v1.6.3","v1.6.2","v1.6.1","v1.6.0","v1.5.5","v1.5.4","v1.5.3","v1.5.2","v1.5.1","v1.5.0","v1.4.0","v1.3.11","v1.3.10","v1.3.9","v1.3.8","v1.3.7","v1.3.6","v1.3.5","v1.3.4","v1.3.3","v1.3.2","v1.3.1","v1.3.0","v1.2.9","v1.2.8","v1.2.7","v1.2.6","1.2.5","1.2.4","1.2.3","1.2.2","1.2.1","1.2.0","1.1.7"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-55187.json"}}],"schema_version":"1.9.0","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N"}]}