Mailpit
CVE-2026-23829
MEDIUM
GHSA-54wq-72mp-cq7c
Severity by source
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Primary rating from GitHub Advisory.
CVSS VectorGitHub Advisory
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N
Lifecycle Timeline
4DescriptionGitHub Advisory
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.
AnalysisAI
Header injection in Mailpit's SMTP server prior to version 1.28.3 allows unauthenticated remote attackers to inject or modify email headers by embedding carriage return characters in sender and recipient addresses due to insufficient regex validation. Public exploit code exists for this vulnerability, which could enable attackers to manipulate email routing, spoofing, or phishing attacks against users of the email testing tool. The issue is resolved in version 1.28.3 and later.
Technical ContextAI
Affects Mailpit. 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 use
RemediationAI
A vendor patch is available — apply it immediately. Restrict network access to the affected service where possible.
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Mailpit versions before 1.28.3 contain a server-side request forgery vulnerability in the HTML Check feature that allows
Cross-site WebSocket hijacking in Mailpit 1.29.0-1.30.5 exposes live email metadata to any website the developer visits,
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Same technique Code Injection
View allVendor StatusVendor
SUSE
Severity: Medium| Product | Status |
|---|---|
| openSUSE Leap 15.6 | Fixed |
| SUSE Linux Enterprise Module for Package Hub 15 SP5 | Fixed |
| SUSE Linux Enterprise Module for Package Hub 15 SP6 | Fixed |
| openSUSE Leap 15.5 | Fixed |
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External POC / Exploit Code
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