CVE-2026-67447
Mailpit: SMTP DATA line reader buffers over-limit input before size enforcement
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.
INFO
Published Date :
Aug. 20, 2026, 10:17 p.m.
Last Modified :
Oct. 18, 2026, 8:10 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS | 134c704f-9b21-4f2e-91b3-4a467353bcc0 | |||||
| CVSS 3.1 | MEDIUM | [email protected] | ||||
| CVSS 3.1 | MEDIUM | MITRE-CVE |
Solution
- Update Mailpit to version 1.30.5.
- Ensure Server.MaxSize is correctly configured.
- Monitor memory usage after update.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-67447.
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-67447 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-67447
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-67447 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-67447 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
CVE Translated by [email protected]
Oct. 18, 2026
Action Type Old Value New Value Added Translation Title: mailpit de axllent, Description: Mailpit es una herramienta de prueba de correo electrónico y API para desarrolladores. Desde la versión 1.30.0 hasta la 1.30.5, la función readData() de internal/smtpd/smtpd.go de Mailpit llama a bufio.Reader.ReadBytes antes de aplicar la verificación de tamaño len(data)+len(line) a la línea SMTP DATA completada contra Server.MaxSize. Un cliente SMTP no autenticado puede enviar una sola línea más grande que el MaxMessageSize configurado, lo que provoca que la línea completa se asigne antes de que Mailpit devuelva el rechazo 552 5.3.4. Esta brecha posterior a la corrección permanece después de que la acumulación normal de DATA de varias líneas fuera limitada, y las líneas sobredimensionadas concurrentes pueden crear una presión de memoria sustancial más allá del límite de tamaño de mensaje configurado. Este problema está solucionado en la versión 1.30.5. -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Aug. 21, 2026
Action Type Old Value New Value Added Reference https://github.com/axllent/mailpit/security/advisories/GHSA-r553-m4fv-5v97 Added SSVC {'id': 'CVE-2026-67447', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'yes'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-08-21T16:18:52.447416Z'} -
New CVE Received by [email protected]
Aug. 20, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'axllent', 'product': 'mailpit', 'versions': [{'status': 'affected', 'version': '>= 1.30.0, < 1.30.5'}]}] Added 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. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L Added CWE CWE-770 Added Reference https://github.com/axllent/mailpit/commit/8720c6bd8281fc00d458081908f1dbef8e59a98c Added Reference https://github.com/axllent/mailpit/releases/tag/v1.30.5 Added Reference https://github.com/axllent/mailpit/security/advisories/GHSA-r553-m4fv-5v97