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Vulnerability · Published Aug 20, 2026 · Assigned by GitHub_M

CVE-2026-67445Mailpit: SMTP command parser buffers unbounded command lines before syntax rejection

Medium 5.3

In plain English

A medium-severity uncontrolled resource consumption in mailpit from axllent. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 43% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)5.3Medium
Exploit odds (30 days)0.5%top 56.6% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Gogithub.com/axllent/mailpit1.30.4GHSA-w878-pj84-3j5v
Gogithub.com/axllent/mailpit1.30.4GO-2026-6363

Affected products (as reported)

VendorProductVersions
axllent mailpit < 1.30.4

Weakness: CWE-400 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

References