Advisories for Golang/Github.com/Axllent/Mailpit package

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. Affected Components Primary File: internal/htmlcheck/css.go (lines 132-207) API Endpoint: /api/v1/message/{ID}/html-check Handler: server/apiv1/other.go (lines 38-75) Vulnerable Functions: inlineRemoteCSS() - line 132 downloadToBytes() - line 193 isURL() - line …

Mailpit's SMTP server is vulnerable to Header Injection due to an insufficient Regular Expression used to validate RCPT TO and MAIL FROM addresses. An attacker can inject arbitrary SMTP headers (or corrupt existing ones) by including carriage return characters (\r) in the email address. This header injection occurs because the regex intended to filter control characters fails to exclude \r and \n when used inside a character class.

Summary The Mailpit WebSocket server is configured to accept connections from any origin. This lack of Origin header validation introduces a Cross-Site WebSocket Hijacking (CSWSH) vulnerability. An attacker can host a malicious website that, when visited by a developer running Mailpit locally, establishes a WebSocket connection to the victim's Mailpit instance (default ws://localhost:8025). This allows the attacker to intercept sensitive data such as email contents, headers, and server statistics in …

A Server-Side Request Forgery (SSRF) vulnerability exists in Mailpit's /proxy endpoint that allows attackers to make requests to internal network resources.