---
id: CVE-2026-67447
title: Mailpit is an email testing tool and API for developers
summary: >-
  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 SMT…
severity: medium
cvss: 5.3
cvssVector: 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L'
cwe:
  - CWE-770
vendor: axllent
product: github.com/axllent/mailpit
affected:
  - 'github.com/axllent/mailpit >= 1.30.0, < 1.30.5'
patched:
  - github.com/axllent/mailpit 1.30.5
published: '2026-08-20'
updated: '2026-09-18'
sourceUpdated: '2026-09-18T20:09:01.757'
source: NVD
sourceUrl: 'https://nvd.nist.gov/vuln/detail/CVE-2026-67447'
references:
  - url: >-
      https://github.com/axllent/mailpit/commit/8720c6bd8281fc00d458081908f1dbef8e59a98c
    label: security-advisories@github.com
  - url: 'https://github.com/axllent/mailpit/releases/tag/v1.30.5'
    label: security-advisories@github.com
  - url: 'https://github.com/axllent/mailpit/security/advisories/GHSA-r553-m4fv-5v97'
    label: security-advisories@github.com
  - url: 'https://github.com/axllent/mailpit/security/advisories/GHSA-r553-m4fv-5v97'
    label: 134c704f-9b21-4f2e-91b3-4a467353bcc0
  - url: 'https://github.com/advisories/GHSA-r553-m4fv-5v97'
tags:
  - nvd
  - ghsa
  - go
epss: 0.00451
epssPercentile: 0.3857
aliases:
  - GHSA-r553-m4fv-5v97
ecosystem: go
ingestedAt: '2026-08-20T22:02:21.064Z'
---

## Overview

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.

## Remediation

Refer to the linked advisories for vendor-supplied fixes and affected version ranges.

## Package advisory (CVE-2026-67447)

Affected packages:

- `github.com/axllent/mailpit >= 1.30.0, < 1.30.5`

Patched in:

- `github.com/axllent/mailpit 1.30.5`

Source: https://github.com/advisories/GHSA-r553-m4fv-5v97