CVE-2026-45712
Mailpit: Concurrent map read & write in proxy CSS rewriter - remote unauth crash (fatal error: concurrent map read and map write)
Description
Mailpit is an email testing tool and API for developers. Prior to version 1.30.0, the screenshot/print proxy (/proxy?data=…) maintains a package-level assets map[string]MessageAssets cache, but reads the map without holding assetsMutex while a long-running cleanup goroutine and (re-entrant) CSS-rewriting code path concurrently write to it under the lock. When the unsynchronized read coincides with a synchronized write, Go's runtime raises fatal error: concurrent map read and map write — a runtime.throw that is not recoverable by http.Server's handler-panic recover. The whole Mailpit process exits, taking the SMTP, POP3 and HTTP listeners down with it. Version 1.30.0 contains a patch.
INFO
Published Date :
July 20, 2026, 4:17 p.m.
Last Modified :
Oct. 24, 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 1.30.0 or later.
- Apply vendor patches if available for older versions.
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-2026-45712.
| URL | Resource |
|---|---|
| https://github.com/axllent/mailpit/releases/tag/v1.30.0 | Release Notes |
| https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722 | Exploit Vendor Advisory |
| https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722 | Exploit Vendor Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-45712 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-2026-45712
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-2026-45712 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-45712 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. 24, 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. Antes de la versión 1.30.0, el proxy de captura de pantalla/impresión (/proxy?data=...) mantiene una caché de activos a nivel de paquete map[string]MessageAssets, pero lee el mapa sin mantener assetsMutex mientras una goroutine de limpieza de larga duración y una ruta de código de reescritura de CSS (reentrante) escriben concurrentemente en él bajo el bloqueo. Cuando la lectura no sincronizada coincide con una escritura sincronizada, el tiempo de ejecución de Go genera un error fatal: lectura concurrente de mapa y escritura de mapa - un runtime.throw que no es recuperable por el recuperador de pánico del gestor del servidor HTTP. Todo el proceso de Mailpit se cierra, llevando consigo los oyentes SMTP, POP3 y HTTP. La versión 1.30.0 contiene un parche. -
Initial Analysis by [email protected]
Jul. 28, 2026
Action Type Old Value New Value Added CPE Configuration OR *cpe:2.3:a:axllent:mailpit:*:*:*:*:*:*:*:* versions up to (excluding) 1.30.0 Added Reference Type GitHub, Inc.: https://github.com/axllent/mailpit/releases/tag/v1.30.0 Types: Release Notes Added Reference Type GitHub, Inc.: https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722 Types: Exploit, Vendor Advisory Added Reference Type CISA-ADP: https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722 Types: Exploit, Vendor Advisory -
New CVE Received by [email protected]
Jul. 20, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'axllent', 'product': 'mailpit', 'versions': [{'status': 'affected', 'version': '< 1.30.0'}]}] Added Description Mailpit is an email testing tool and API for developers. Prior to version 1.30.0, the screenshot/print proxy (/proxy?data=…) maintains a package-level assets map[string]MessageAssets cache, but reads the map without holding assetsMutex while a long-running cleanup goroutine and (re-entrant) CSS-rewriting code path concurrently write to it under the lock. When the unsynchronized read coincides with a synchronized write, Go's runtime raises fatal error: concurrent map read and map write — a runtime.throw that is not recoverable by http.Server's handler-panic recover. The whole Mailpit process exits, taking the SMTP, POP3 and HTTP listeners down with it. Version 1.30.0 contains a patch. Added CVSS V3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H Added CWE CWE-362 Added CWE CWE-770 Added Reference https://github.com/axllent/mailpit/releases/tag/v1.30.0 Added Reference https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722 -
CVE Modified by 134c704f-9b21-4f2e-91b3-4a467353bcc0
Jul. 20, 2026
Action Type Old Value New Value Added Reference https://github.com/axllent/mailpit/security/advisories/GHSA-w4vj-r5pg-3722 Added SSVC {'id': 'CVE-2026-45712', 'role': 'CISA Coordinator', 'options': [{'exploitation': 'poc'}, {'automatable': 'no'}, {'technicalImpact': 'partial'}], 'version': '2.0.3', 'timestamp': '2026-07-20T15:32:57.656933Z'}