{"cve":"CVE-2026-45709","nvd":{"published":"2026-07-20T16:17:00.190","modified":"2026-10-24T20:10:00.137","status":"Analyzed","description":"Mailpit is an email testing tool and API for developers. The fix for GHSA-6jxm-fv7w-rw5j (CVE-2026-23845, \"Server-Side Request Forgery (SSRF) via HTML Check API\"), shipped in mailpit `v1.28.3`, hardened `internal/htmlcheck/css.go::downloadCSSToBytes` with a 5MB size cap, a `text/css` content-type check, login-info stripping in `isValidURL`, and an opt-in `--block-remote-css-and-fonts` config flag — but did not add the IP-filtering dialer that the same codebase already uses on the two sister SSRF endpoints (the proxy handler and link-check). Prior to version 1.30.0, `internal/htmlcheck/css.go::newSafeHTTPClient` is mis-named — it builds an `http.Client` whose `Transport.DialContext` calls `net.Dialer.DialContext` directly with no IP allowlisting. As a result, the SSRF originally reported by Bao Anh Phan still permits the server to dial loopback, private, link-local, and any other reserved/multicast range, provided the target replies with `HTTP/200` and a content-type beginning with `text/css`. With redirect-following (`CheckRedirect` allows redirects to any `isValidURL` URL with no IP filter), an attacker-controlled public site can redirect mailpit's request into the private network without ever appearing in the email's HTML. In the default mailpit deploy (no UI auth, no SMTP auth, port 1025/8025 exposed), this is an unauthenticated, network-reachable SSRF triggered by sending an HTML email and then issuing one HTTP `GET` to `/api/v1/message/{id}/html-check`. Version 1.30.0 contains an updated fix.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","score":5.8},"cwes":["CWE-918"],"references":["https://github.com/axllent/mailpit/releases/tag/v1.30.0","https://github.com/axllent/mailpit/security/advisories/GHSA-j3fj-qppj-fmmc"],"products":["axllent:mailpit"],"source":"nvd","synced_at":"2026-10-25T17:50:08.599881581+00:00"},"epss":{"cve":"CVE-2026-45709","score":0.00316,"percentile":0.24242,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-j3fj-qppj-fmmc","url":"https://osv.dev/vulnerability/GHSA-j3fj-qppj-fmmc","summary":"Mailpit has an incomplete fix for GHSA-6jxm: HTML check still permits SSRF to private/loopback/IMDS via missing IP-filter dialer","modified":"2026-09-02T23:45:04.685651976Z","packages":[{"ecosystem":"Go","name":"github.com/axllent/mailpit","purl":"pkg:golang/github.com/axllent/mailpit","ranges":[">=1.28.3 <1.30.0"],"fixed":["1.30.0"]}]},{"id":"GO-2026-5446","url":"https://osv.dev/vulnerability/GO-2026-5446","summary":"Mailpit has an incomplete fix for GHSA-6jxm: HTML check still permits SSRF to private/loopback/IMDS via missing IP-filter dialer in github.com/axllent/mailpit","modified":"2026-06-25T23:01:18.194823355Z","packages":[{"ecosystem":"Go","name":"github.com/axllent/mailpit","purl":"pkg:golang/github.com/axllent/mailpit","ranges":[">=1.28.3 <1.30.0"],"fixed":["1.30.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}