knadh listmonk up to 5.0.1 Environment Variable env/expandenv special elements used in a template engine

Summaryinfo

A vulnerability was found in knadh listmonk up to 5.0.1. It has been rated as problematic. This affects the function env/expandenv of the component Environment Variable Handler. This manipulation causes improper neutralization of special elements used in a template engine. This vulnerability is handled as CVE-2025-49136. The attack can be initiated remotely. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in knadh listmonk up to 5.0.1. It has been declared as problematic. Affected by this vulnerability is the function env/expandenv of the component Environment Variable Handler. The manipulation with an unknown input leads to a improper neutralization of special elements used in a template engine vulnerability. The CWE definition for the vulnerability is CWE-1336. The product uses a template engine to insert or process externally-influenced input, but it does not neutralize or incorrectly neutralizes special elements or syntax that can be interpreted as template expressions or other code directives when processed by the engine. As an impact it is known to affect confidentiality, integrity, and availability. The summary by CVE is:

listmonk is a standalone, self-hosted, newsletter and mailing list manager. Starting in version 4.0.0 and prior to version 5.0.2, the `env` and `expandenv` template functions which is enabled by default in Sprig enables capturing of env variables on host. While this may not be a problem on single-user (super admin) installations, on multi-user installations, this allows non-super-admin users with campaign or template permissions to use the `{{ env }}` template expression to capture sensitive environment variables. Users should upgrade to v5.0.2 to mitigate the issue.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2025-49136 since 06/02/2025. The exploitation appears to be easy. The attack can be launched remotely. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1221 according to MITRE ATT&CK.

Upgrading to version 5.0.2 eliminates this vulnerability. The upgrade is hosted for download at github.com. Applying the patch d27d2c32cf3af2d0b24e29ea5a686ba149b49b3e is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• knadh

Name

• listmonk

Version

• 5.0.0
• 5.0.1

License

• open-source

Website

• Product: https://github.com/knadh/listmonk/

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