Stored-header corruption via SMTP address regex
Published Jan 18, 2026 · Updated Jan 18, 2026
SMTP header injection in Axllent Mailpit before 1.28.3 allows remote attackers to corrupt stored email headers through crafted addresses. The RCPT TO and MAIL FROM parsers use a character class that excludes vertical tab but accepts carriage returns later embedded in Received headers. The SMTP listener must be reachable; no authentication or user interaction is required, and the demonstrated consequence is stored-message integrity loss.
Summary
What happened
SMTP header injection in Axllent Mailpit before 1.28.3 allows remote attackers to corrupt stored email headers through crafted addresses. The RCPT TO and MAIL FROM parsers use a character class that excludes vertical tab but accepts carriage returns later embedded in Received headers. The SMTP listener must be reachable; no authentication or user interaction is required, and the demonstrated consequence is stored-message integrity loss.
The record
- CVE
- CVE-2026-23829
- Published
- Jan 18, 2026
- Updated
- Jan 18, 2026
- Vendor
- Axllent
- Product
- Mailpit
- Classifications
- CWE-93, CWE-150, CAPEC-106
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jan 18, 2026CVE publishedPublication date reported by the CVE source.
- Jan 18, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=< 1.28.3
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-54wq-72mp-cq7c SMTP carriage-return proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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