What’s Vulnerable › Vulnerabilities

CVE-2026-67447: Mailpit: SMTP DATA line reader buffers over-limit input before size enforcement

• Severity: medium (CVSS 5.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.5% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-20 · updated 2026-10-18
• Weakness: CWE-770

Description

Mailpit is an email testing tool and API for developers. From 1.30.0 until 1.30.5, Mailpit's internal/smtpd/smtpd.go readData() function calls bufio.Reader.ReadBytes before applying the len(data)+len(line) size check to the completed SMTP DATA line against Server.MaxSize. An unauthenticated SMTP client can send a single line larger than the configured MaxMessageSize, causing the full line to be allocated before Mailpit returns the 552 5.3.4 rejection. This post-fix gap remains after normal multi-line DATA accumulation was bounded, and concurrent oversized lines can create substantial memory pressure beyond the configured message-size cap. This issue is fixed in version 1.30.5.

Affected products

• axllent mailpit: from 1.30.0, < 1.30.5

References

• https://github.com/axllent/mailpit/commit/8720c6bd8281fc00d458081908f1dbef8e59a98c
• https://github.com/axllent/mailpit/releases/tag/v1.30.5
• https://github.com/axllent/mailpit/security/advisories/GHSA-r553-m4fv-5v97
• https://github.com/axllent/mailpit/security/advisories/GHSA-r553-m4fv-5v97

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