CVE-2026-21859: Axllent Mailpit

Medium severity, CVSS 5.3. EPSS: 0.8% chance of exploitation in the next 30 days.

Mailpit is an email testing tool and API for developers. Versions 1.28.0 and below have a Server-Side Request Forgery (SSRF) vulnerability in the /proxy endpoint, allowing attackers to make requests to internal network resources. The /proxy endpoint validates http:// and https:// schemes, but it does not block internal IP addresses, enabling attackers to access internal services and APIs. This vulnerability is limited to HTTP GET requests with minimal headers. The issue is fixed in version 1.28.1.

Affected products

• Axllent Mailpit: before 1.28.1 (fixed in 1.28.1)

Published 2026-01-08. Last modified 2026-06-17.