CVE-2026-23845CWE-918

Mailpit Vulnerable to Server-Side Request Forgery (SSRF) via HTML Check API

Medium · published January 19, 2026

CVSS v3.1
5.8
EPSS
0%
Percentile
36.3
In the wild
Unconfirmed
What it is

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.

The record
Technical detail
CVSS v3.1
5.8 · MEDIUM
Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N
CVSS v4.0
Not supplied
EPSS
0.00431 · 36.3th percentile
Weakness
CWE-918 · Server-Side Request Forgery (SSRF)
Published
2026-01-19T19:01Z
EPSS history
Timeline
  • 19 JAN 19:01Z
    Mailpit Vulnerable to Server-Side Request Forgery (SSRF) via HTML Check API
    cvelistv5