CVE-2026-23829: Mailpit has SMTP Header Injection via Regex Bypass
axllent · mailpit
Affected: axllent mailpit · Exploitation: check available, not yet exploited
Not in CyberSIXT coverage yet: no article names this CVE. This page shows the public record.
Higher than 72% of scored CVEs
DescriptionCVE.org
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 products1
From the CVE record. A product or version that is not listed is unknown, not unaffected.
- axllent · mailpit< 1.28.3
On the Atlas
Every published CVE is on the CyberSIXT Atlas, grouped by weakness, vendor and month.
- Exploitation
- Check available, not yet exploited. A public nuclei template can confirm it on a system you are authorised to test.
- CISA KEV
- Not listed
- Public check
- Mailpit < 1.28.2 - SMTP CRLF Injection · nuclei template in projectdiscovery/nuclei-templates
- Vendor
- axllent
- Published
- January 2026
CoverageNo articles yet
No CyberSIXT article names CVE-2026-23829 yet, so there is no coverage timeline, action brief or change log for it. Everything on this page comes from the public CVE record, CISA KEV, EPSS and the nuclei template index. Search the archive or see the CVEs in the news.