CVE-2026-55187

What it is

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.

At a glance

Exploitability

Can be exploited over the network without logging in. Limited direct impact.

Exploit odds

0.4% chance of exploitation in the next 30 days (EPSS).

Fix

A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

1. 2026-07-10 22:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2. 2026-10-25 15:10 UTC Last updatedMost recent change to the record

Why it ranks here

• Exploited in the wild: no, CISA does not list it.
• Exploit odds: 0.4% in the next 30 days (EPSS).
• Severity: 5.8 MEDIUM (CVSS).
• Fix: a patch or advisory is linked.

Details

Published

2026-07-10 22:16 UTC

Last modified

2026-10-25 15:10 UTC

Exploit probability

0.4% · EPSS, next 30 days

Weakness

CWE-918 · Server-side request forgery

Record status

Deferred

Attack profile CVSS 3.1 · 5.8

Attack vector

Network

Complexity

Low

Privileges needed

None

User interaction

None

Scope

Changed

Confidentiality

Low

Integrity

None

Availability

None

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-55187.md and follow it. Check whether this project is affected by CVE-2026-55187. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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