CVE-2026-21859: axllent mailpit Server-Side Request Forgery (SSRF)

Vulnerability summary

CVE-2026-21859 is a medium (CVSS 5.8) Server-Side Request Forgery (SSRF) vulnerability in axllent mailpit. EPSS estimates a 0.81% chance of exploitation in the next 30 days, higher than 56.2% of scored vulnerabilities. 1 public exploit is recorded.

Timeline

1. 07-01-2026
   PublishedVulnerability first disclosed.
2. 08-01-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-918Server-Side Request Forgery (SSRF)The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.