CVE-2025-49136: listmonk's Sprig template Injection vulnerability leads to reading of Environment Variable for low privilege user

Vulnerability summary

CVE-2025-49136 is a critical (CVSS 9.1) vulnerability in knadh listmonk. EPSS estimates a 1.58% chance of exploitation in the next 30 days, higher than 75.5% of scored vulnerabilities. 2 public exploits are recorded.

Timeline

1. 09-06-2025
   PublishedVulnerability first disclosed.
2. 10-06-2025
   Last modifiedVulnerability information updated.

Description

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.

• CWE-1336Improper Neutralization of Special Elements Used in a Template EngineThe 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.