CVE-2026-67445

MEDIUM 5.3

Mailpit: SMTP command parser buffers unbounded command lines before syntax rejection

CVSS Score

5.3

EPSS Score

0.0%

EPSS Percentile

0th

Mailpit is an email testing tool and API for developers. Prior to 1.30.4, Mailpit reads SMTP commands through internal/smtpd/smtpd.go session.readLine() using bufio.Reader.ReadString before session.parseLine() parses the verb or the RFC 5321 512-octet command-line limit is enforced. An unauthenticated remote SMTP client can send an oversized single command line that is fully allocated before syntax rejection or timeout, and the normal MaxMessageSize and DATA limits do not apply to this pre-DATA path. The same command reader is used by handleAuthLogin(), handleAuthPlain(), and handleAuthCramMD5() continuation lines, so concurrent oversized inputs can create memory pressure and reduce service availability. This issue is fixed in version 1.30.4.

CWE	CWE-400
Vendor	axllent
Product	mailpit
Published	Aug 20, 2026

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CVSS v3 Breakdown

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

Attack Vector

Network

Attack Complexity

Low

Privileges Required

None

User Interaction

None

Scope

Unchanged

Confidentiality

None

Integrity

None

Availability

Low

Affected Versions

axllent / mailpit

< 1.30.4

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/axllent/mailpit/security/advisories/GHSA-w878-pj84-3j5v github.com: https://github.com/axllent/mailpit/commit/993bed95b3c74d95231af93bd0e0d4c3d5b4db4d github.com: https://github.com/axllent/mailpit/releases/tag/v1.30.4