VulnerabilityDeferred

CVE-2026-55187

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,…

MEDIUM 5.8EPSS 0.38%

Does this matter?

Lower severity and a low EPSS score (0.38%). Track it; it rarely justifies an emergency change on its own.

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.

CVSS 3.1: 5.8 MEDIUMCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
EPSS: 0.38% probability · 32th percentile
CISA KEV: Not listed
Weakness: CWE-918
Source: security-advisories@github.com

References

Source: NVD record, EPSS from FIRST.org, KEV from CISA. Refreshed daily.