CVE-2025-49136

Comprehensive Technical Analysis of CVE-2025-49136

1. Vulnerability Assessment and Severity Evaluation

CVE ID: CVE-2025-49136 CVSS Score: 9

Severity Evaluation: The CVSS score of 9 indicates a critical vulnerability. This high score is justified by the potential for unauthorized access to sensitive environment variables, which can lead to significant security breaches. The vulnerability allows non-super-admin users to capture environment variables, which may include sensitive information such as API keys, database credentials, and other configuration details.

2. Potential Attack Vectors and Exploitation Methods

Attack Vectors:

• Multi-User Environments: The primary attack vector is in multi-user installations where non-super-admin users have campaign or template permissions. These users can exploit the {{ env }} template expression to capture environment variables.
• Template Injection: The vulnerability leverages the env and expandenv template functions in Sprig, which are enabled by default. An attacker can inject these expressions into templates to extract sensitive information.

Exploitation Methods:

• Template Manipulation: An attacker with template permissions can insert the {{ env }} expression into a template. When the template is processed, it captures the environment variables.
• Campaign Manipulation: Similarly, an attacker with campaign permissions can embed the {{ env }} expression into campaign content to achieve the same result.

3. Affected Systems and Software Versions

Affected Software:

• listmonk: Versions 4.0.0 to 5.0.1

Affected Systems:

• Any system running the affected versions of listmonk, particularly in multi-user environments where non-super-admin users have template or campaign permissions.

4. Recommended Mitigation Strategies

Immediate Mitigation:

• Upgrade: Upgrade to listmonk version 5.0.2 or later, which includes a patch for this vulnerability.
• Disable Template Functions: If upgrading is not immediately possible, disable the env and expandenv template functions in Sprig.

Long-Term Mitigation:

• Regular Audits: Conduct regular security audits of templates and campaigns to ensure no malicious expressions are present.
• Least Privilege: Implement the principle of least privilege, ensuring that users have the minimum permissions necessary to perform their tasks.
• Environment Segmentation: Segregate sensitive environment variables from non-sensitive ones and restrict access to sensitive variables.

5. Impact on Cybersecurity Landscape

Broader Implications:

• Data Breaches: The vulnerability can lead to data breaches, as sensitive environment variables may include credentials and configuration details that can be used to access other systems.
• Trust and Reputation: Organizations using listmonk may face reputational damage if a breach occurs due to this vulnerability.
• Compliance: Failure to address this vulnerability can result in non-compliance with data protection regulations, leading to legal and financial penalties.

6. Technical Details for Security Professionals

Technical Overview:

• Template Engine: The vulnerability is rooted in the Sprig template engine, which includes the env and expandenv functions. These functions allow templates to capture environment variables.
• Default Configuration: The env and expandenv functions are enabled by default, making them a potential risk in multi-user environments.
• Patch Details: The patch in version 5.0.2 disables these functions by default, requiring explicit configuration to re-enable them.

Detection and Monitoring:

• Log Analysis: Monitor logs for unusual template or campaign modifications, especially those involving the {{ env }} expression.
• Intrusion Detection: Implement intrusion detection systems (IDS) to detect and alert on suspicious activities related to template and campaign modifications.

Incident Response:

• Containment: Immediately disable the env and expandenv functions if an exploit is detected.
• Forensics: Conduct a thorough forensic analysis to determine the extent of the breach and identify any compromised environment variables.
• Remediation: Upgrade to the patched version and review all templates and campaigns for malicious expressions.

Conclusion: CVE-2025-49136 represents a critical vulnerability in listmonk that can be exploited in multi-user environments. Immediate mitigation through upgrading to version 5.0.2 or disabling the affected template functions is essential. Long-term strategies include regular audits, implementing least privilege, and environment segmentation to enhance overall security.

References:

• Patch Commit
• Release Notes
• Vendor Advisory