{"id":"CVE-2026-45709","sourceIdentifier":"security-advisories@github.com","published":"2026-07-20T16:17:00.190","lastModified":"2026-10-24T20:10:00.137","vulnStatus":"Analyzed","cveTags":[],"descriptions":[{"lang":"en","value":"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."},{"lang":"es","value":"Mailpit es una herramienta de prueba de correo electrónico y API para desarrolladores. La corrección para GHSA-6jxm-fv7w-rw5j (CVE-2026-23845, ’Falsificación de petición del lado del servidor (SSRF) a través de la API de verificación de HTML’), incluida en mailpit ’v1.28.3’, reforzó ’internal/htmlcheck/css.go::downloadCSSToBytes’ con un límite de tamaño de 5MB, una verificación de tipo de contenido ’text/css’, la eliminación de información de inicio de sesión en ’isValidURL’, y un indicador de configuración opcional ’--block-remote-css-and-fonts’ - pero no añadió el marcador de filtrado de IP que el mismo código base ya utiliza en los dos puntos finales SSRF hermanos (el gestor de proxy y la verificación de enlaces). Antes de la versión 1.30.0, ’internal/htmlcheck/css.go::newSafeHTTPClient’ está mal nombrado - construye un ’http.Client’ cuyo ’Transport.DialContext’ llama a ’net.Dialer.DialContext’ directamente sin lista blanca de IP. Como resultado, la SSRF originalmente reportada por Bao Anh Phan todavía permite al servidor marcar rangos de loopback, privados, de enlace local y cualquier otro rango reservado/multicast, siempre que el objetivo responda con ’HTTP/200’ y un tipo de contenido que comience con ’text/css’. Con el seguimiento de redirecciones (’CheckRedirect’ permite redirecciones a cualquier URL ’isValidURL’ sin filtro de IP), un sitio público controlado por el atacante puede redirigir la petición de mailpit a la red privada sin aparecer nunca en el HTML del correo electrónico. En el despliegue predeterminado de mailpit (sin autenticación de UI, sin autenticación SMTP, puerto 1025/8025 expuesto), esta es una SSRF no autenticada y accesible por red, activada al enviar un correo electrónico HTML y luego emitiendo una petición HTTP ’GET’ a ’/api/v1/message/{id}/html-check’. La versión 1.30.0 contiene una corrección actualizada."}],"affected":[{"source":"security-advisories@github.com","affectedData":[{"vendor":"axllent","product":"mailpit","versions":[{"version":">= 1.28.3, < 1.30.0","status":"affected"}]}]}],"metrics":{"cvssMetricV31":[{"source":"security-advisories@github.com","type":"Secondary","cvssData":{"version":"3.1","vectorString":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N","baseScore":5.8,"baseSeverity":"MEDIUM","attackVector":"NETWORK","attackComplexity":"LOW","privilegesRequired":"NONE","userInteraction":"NONE","scope":"CHANGED","confidentialityImpact":"NONE","integrityImpact":"LOW","availabilityImpact":"NONE"},"exploitabilityScore":3.9,"impactScore":1.4}],"ssvcV203":[{"source":"134c704f-9b21-4f2e-91b3-4a467353bcc0","ssvcData":{"timestamp":"2026-07-20T19:01:39.446033Z","id":"CVE-2026-45709","options":[{"exploitation":"none"},{"automatable":"yes"},{"technicalImpact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}]},"weaknesses":[{"source":"security-advisories@github.com","type":"Secondary","description":[{"lang":"en","value":"CWE-918"}]}],"configurations":[{"nodes":[{"operator":"OR","negate":false,"cpeMatch":[{"vulnerable":true,"criteria":"cpe:2.3:a:axllent:mailpit:*:*:*:*:*:*:*:*","versionStartIncluding":"1.28.3","versionEndExcluding":"1.30.0","matchCriteriaId":"9A926FB6-37C0-4810-A70C-97FD072553D3"}]}]}],"references":[{"url":"https://github.com/axllent/mailpit/releases/tag/v1.30.0","source":"security-advisories@github.com","tags":["Release Notes"]},{"url":"https://github.com/axllent/mailpit/security/advisories/GHSA-j3fj-qppj-fmmc","source":"security-advisories@github.com","tags":["Exploit","Vendor Advisory"]}]}