CVE-2026-23845 | THREATINT

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.

PUBLISHED Reserved 2026-01-16 | Published 2026-01-19 | Updated 2026-01-20 | Assigner GitHub_M

MEDIUM: 5.8CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:N

Problem types

CWE-918: Server-Side Request Forgery (SSRF)

Product status

< 1.28.3

affected

References

github.com/...ailpit/security/advisories/GHSA-6jxm-fv7w-rw5j

github.com/...ommit/1679a0aba592ebc8487a996d37fea8318c984dfe

github.com/axllent/mailpit/releases/tag/v1.28.3

cve.org (CVE-2026-23845)

nvd.nist.gov (CVE-2026-23845)

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