CVE-2026-23829

Summary

Mailpit is an email testing tool and API for developers. Prior to version 1.28.3, 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. Version 1.28.3 fixes this issue.

Affected Software

VendorProductVersion RangeStatus
axllentmailpit< 1.28.3affected

Weaknesses

  • CWE-93: CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection')
  • CWE-150: CWE-150: Improper Neutralization of Escape, Meta, or Control Sequences

ADP Enrichment

CISA ADP Vulnrichment

  • SSVC:
  • Exploitation: poc
    • Automatable: yes
    • Technical Impact: partial

References