Resource exhaustion in Axllent Mailpit
CVE-2026-67447
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.
CVSS v3 metric
CVSS v3 base score 5.3 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L.
Affected products
- Axllent Mailpit — versions >= 1.30.0, < 1.30.5
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-67447?
- CVE-2026-67447 is a medium-severity vulnerability in Axllent Mailpit, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 5.3/10. Published 2026-08-20.
- How severe is CVE-2026-67447?
- Medium severity. CVSS v3 base score is 5.3 out of 10.