EUVD-2025-31664

Comprehensive Technical Analysis of EUVD-2025-31664

1. Vulnerability Assessment and Severity Evaluation

The vulnerability described in EUVD-2025-31664 affects the serverless-dns resolver, which is deployed on various cloud platforms including Cloudflare Workers, Deno Deploy, Fastly, and Fly.io. The issue lies in the pr.yml GitHub Action, which unsafely interpolates untrusted input into a command executed by the runner. This vulnerability allows an unauthorized attacker to push arbitrary data to the repository, potentially leading to code execution.

Severity Evaluation:

• Base Score: 9.3 (CVSS 4.0)
• Vector String: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H/E:P

The high base score indicates a critical vulnerability due to the potential for high confidentiality, integrity, and availability impacts, as well as the ease of exploitation.

2. Potential Attack Vectors and Exploitation Methods

Attack Vectors:

• Untrusted Input Interpolation: The primary attack vector involves the unsafe interpolation of untrusted input (github.event.pull_request.head.repo.clone_url and github.head_ref) into a command executed by the GitHub Action runner.
• Permissive Permissions: The use of the pull_request_target trigger grants permissive permissions, allowing the attacker to exploit the vulnerability more easily.

Exploitation Methods:

• Arbitrary Data Push: An attacker can craft a malicious pull request that, when processed by the vulnerable GitHub Action, pushes arbitrary data to the repository.
• Code Execution: By pushing malicious code, the attacker can ensure that this code is executed when serverless-dns is run, leading to further compromise.

3. Affected Systems and Software Versions

Affected Systems:

• Cloud platforms where serverless-dns is deployed: Cloudflare Workers, Deno Deploy, Fastly, and Fly.io.

Affected Software Versions:

• serverless-dns versions through and including 0.1.30.

4. Recommended Mitigation Strategies

Immediate Mitigation:

• Update to the Latest Version: Upgrade to serverless-dns version 0.1.31 or later, which includes the fix for this vulnerability (commit c5537dd).
• Disable Vulnerable GitHub Actions: Temporarily disable or modify the pr.yml GitHub Action to prevent untrusted input interpolation until the update is applied.

Long-Term Mitigation:

• Code Review and Auditing: Conduct thorough code reviews and security audits of GitHub Actions and other CI/CD pipelines to identify and mitigate similar vulnerabilities.
• Least Privilege Principle: Ensure that GitHub Actions and other automation tools operate with the least privilege necessary to minimize the impact of potential vulnerabilities.

5. Impact on European Cybersecurity Landscape

The vulnerability in serverless-dns poses a significant risk to organizations using this resolver, particularly those in the European Union. The potential for arbitrary code execution can lead to data breaches, unauthorized access, and service disruptions. Given the widespread use of cloud platforms and CI/CD pipelines, this vulnerability underscores the importance of robust security practices in DevOps environments.

6. Technical Details for Security Professionals

Vulnerability Details:

• Unsafe Interpolation: The pr.yml GitHub Action unsafely interpolates github.event.pull_request.head.repo.clone_url and github.head_ref into a command.
• Permissive Permissions: The pull_request_target trigger grants permissive permissions, allowing the attacker to exploit the vulnerability.

Fix Details:

• Commit: c5537dd
• Release Version: 0.1.31

References:

• GitHub Security Advisory
• Fix Commit

Additional Recommendations:

• Monitoring and Logging: Implement comprehensive monitoring and logging for GitHub Actions and other CI/CD pipelines to detect and respond to suspicious activities.
• Security Training: Provide regular security training for developers and DevOps teams to ensure awareness of common vulnerabilities and best practices.

By addressing this vulnerability promptly and implementing robust security measures, organizations can mitigate the risk and enhance their overall cybersecurity posture.