What’s Vulnerable › Vulnerabilities

CVE-2026-23845: Mailpit Vulnerable to Server-Side Request Forgery (SSRF) via HTML Check API

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.4% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2026-01-19 · updated 2026-06-17
• Weakness: CWE-918

Description

Mailpit is an email testing tool and API for developers. Versions prior to 1.28.3 are vulnerable to Server-Side Request Forgery (SSRF) via HTML Check CSS Download. The HTML Check feature (`/api/v1/message/{ID}/html-check`) is designed to analyze HTML emails for compatibility. During this process, the `inlineRemoteCSS()` function automatically downloads CSS files from external `<link rel="stylesheet" href="...">` tags to inline them for testing. Version 1.28.3 fixes the issue.

Affected products

• axllent mailpit: before 1.28.3 — fixed in 1.28.3

How to fix

Upgrade to a fixed version: axllent mailpit 1.28.3. Check the vendor advisory for mitigations.

References

• https://github.com/axllent/mailpit/commit/1679a0aba592ebc8487a996d37fea8318c984dfe
• https://github.com/axllent/mailpit/releases/tag/v1.28.3
• https://github.com/axllent/mailpit/security/advisories/GHSA-6jxm-fv7w-rw5j

Get alerted when CVE-2026-23845 or the next vulnerability affects your stack