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CVE-2026-55187

5.8 · MEDIUM

Mailpit is an email testing tool and API for developers.

Published Jul 10, 2026CWE-918EPSS 0.38%

Overview

CVE-2026-55187 is a medium-severity vulnerability. It was published on July 10, 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. 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.

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/commit/a88dadbbe1df016a35a445089ef2a362a6c2de78GitHubgithub.com/axllent/mailpit/releases/tag/v1.30.2GitHubgithub.com/axllent/mailpit/security/advisories/GHSA-w4mc-hhc6-xp28GitHubgithub.com/axllent/mailpit/security/advisories/GHSA-w4mc-hhc6-xp28

How CyberStrike helps

Frequently asked questions

What is CVE-2026-55187?

CVE-2026-55187 is a medium-severity vulnerability. It was published on July 10, 2026 and has a CVSS 3.1 base score of 5.8 (MEDIUM).

How severe is CVE-2026-55187?

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-2026-55187?

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-2026-55187?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-55187 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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