CVE-2026-23845
Medium
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.
SeverityMedium
CVSS5.8
Exploit probability—
ProductAxllent Mailpit
PublishedJan 19, 2026
First seenJan 19, 2026
Weakness typeCWE-918Server-side request forgery (SSRF)
How to fix
Update
- axllent mailpit1.28.3 or later
- github.com/axllent/mailpit1.28.3 or later
Affected products
| Product | Affected versions | Fixed in |
|---|---|---|
| axllent mailpit | v < 1.28.3 | 1.28.3 |
| github.com/axllent/mailpitGo | v < 1.28.3 | 1.28.3 |
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