CVE-2025-49136

The env and expandenv template functions which is enabled by default in Sprig enables capturing of env variables on the 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.

Upgrade to v5.0.2 to mitigate.

Demonstration

Description

A critical template injection vulnerability exists in Listmonk's campaign preview functionality that allows authenticated users with minimal privileges (campaigns:get & campaigns:get_all) to extract sensitive system data, including database credentials, SMTP passwords, and admin credentials due to some dangerous function being allowed.

Proof of Concept

• Create a user and give him campaigns:get and campaigns:get_all privileges

• Now login with that user, go to any campaign, go the Content section and here lies the vulnerability, we're able to execute template content which allows us to get environment variables, execute Sprig functions...

• Now in the text field you can input the following and press Preview:

{{ env "AWS_KEY" }}
{{ env "LISTMONK_db__user" }}
{{ env "LISTMONK_db__password" }}

Preview:

I had the AWS_KEY variable set like that to confirm the vulnerability:

• Through these environment variables the attacker can access, they can fully compromise the database, cloud accounts, admin credentials, and more depending on what was setup leading to total system takeover and data breach.

CVE-2025-49136 has a CVSS score of 9.0 (Critical). The vector is network-reachable, low privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (5.0.2); upgrading removes the vulnerable code path.

Kodem intelligence

• Blacklist some function for templates like env, expandEnv and fail as they can be used to leak environment variables which leads to a full takeover.

1. What is CVE-2025-49136? CVE-2025-49136 is a critical-severity security vulnerability in github.com/knadh/listmonk (go), affecting versions >= 4.0.0, < 5.0.2. It is fixed in 5.0.2.
2. How severe is CVE-2025-49136? CVE-2025-49136 has a CVSS score of 9.0 (Critical). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/knadh/listmonk are affected by CVE-2025-49136? github.com/knadh/listmonk (go) versions >= 4.0.0, < 5.0.2 is affected.
4. Is there a fix for CVE-2025-49136? Yes. CVE-2025-49136 is fixed in 5.0.2. Upgrade to this version or later.
5. Is CVE-2025-49136 exploitable, and should I be worried? Whether CVE-2025-49136 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-49136 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-49136? Upgrade github.com/knadh/listmonk to 5.0.2 or later.