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Description

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.

PUBLISHED Reserved 2026-01-16 | Published 2026-01-18 | Updated 2026-01-19 | Assigner GitHub_M




MEDIUM: 5.3CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

Problem types

CWE-93: Improper Neutralization of CRLF Sequences ('CRLF Injection')

CWE-150: Improper Neutralization of Escape, Meta, or Control Sequences

Product status

< 1.28.3
affected

References

github.com/...ailpit/security/advisories/GHSA-54wq-72mp-cq7c

github.com/...ommit/36cc06c125954dec6673219dafa084e13cc14534

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

cve.org (CVE-2026-23829)

nvd.nist.gov (CVE-2026-23829)

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