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CVE-2026-45709

5.8 · MEDIUM

Mailpit is an email testing tool and API for developers.

Published Jul 20, 2026CWE-918EPSS 0.32%

Overview

CVE-2026-45709 is a medium-severity vulnerability. It was published on July 20, 2026 and has a CVSS 3.1 base score of 5.8 (MEDIUM).

This vulnerability has a CVSS 3.1 base score of 5.8, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

Technical 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 `tex

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/axllent/mailpit/releases/tag/v1.30.0GitHubgithub.com/axllent/mailpit/security/advisories/GHSA-j3fj-qppj-fmmc

How CyberStrike helps

Frequently asked questions

What is CVE-2026-45709?

CVE-2026-45709 is a medium-severity vulnerability. It was published on July 20, 2026 and has a CVSS 3.1 base score of 5.8 (MEDIUM).

How severe is CVE-2026-45709?

This vulnerability has a CVSS 3.1 base score of 5.8, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.

How do I fix or remediate CVE-2026-45709?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-45709?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-45709 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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