Spoofing Nuclei’s Template Verification
Overview
Nuclei, a popular vulnerability scanning tool, has over 21,000 stars on GitHub and over 2.1 million downloads. The tool relies on “templates,” in the form of YAML files, to define specific checks or tests for the scanning process. Ensuring the authenticity of these templates is crucial to avoid tampered or malicious templates that can compromise the scanning process.
Template Verification Process
Nuclei uses a Go regex-based signature verification process to ensure the authenticity of its templates. However, a flaw in this process has been discovered, which allows attackers to inject malicious content into a template while keeping the signature valid for the harmless portion of the template.
Discrepancy in Newline Character Handling
The flaw stems from a discrepancy between how the signature verification process and the YAML parser handle newline characters. Go’s verification logic considers “r” as part of the same line, whereas the YAML parser treats it as a line break. This discrepancy creates an opportunity for attackers to insert malicious codes.
Flawed Processing of Multiple Signature Lines
Additionally, Nuclei’s processing of multiple signature lines “digest:” is flawed, which can also lead to an attacker injecting malicious content into a template. This vulnerability can be exploited to compromise the scanning process and potentially lead to further attacks.
Impact
The discovery of this flaw highlights the importance of ensuring the authenticity of templates in vulnerability scanning tools. If left unaddressed, this vulnerability can lead to:
* Tampered or malicious templates that can compromise the scanning process
* Insertion of malicious content into templates
* Potential exploitation of vulnerabilities in the scanning process
Conclusion
In conclusion, the discovery of this flaw in Nuclei’s template verification process underscores the need for robust security measures in vulnerability scanning tools. It is essential to address this vulnerability to ensure the integrity and authenticity of templates and prevent potential attacks.
FAQs
Q: What is Nuclei?
A: Nuclei is a popular vulnerability scanning tool with over 21,000 stars on GitHub and over 2.1 million downloads.
Q: What is the purpose of template verification in Nuclei?
A: Template verification is used to ensure the authenticity of YAML files that define specific checks or tests for the scanning process.
Q: What is the flaw in Nuclei’s template verification process?
A: The flaw stems from a discrepancy between how the signature verification process and the YAML parser handle newline characters, as well as flawed processing of multiple signature lines “digest:”.
Q: What are the potential consequences of this flaw?
A: The flaw can lead to tampered or malicious templates, insertion of malicious content into templates, and potential exploitation of vulnerabilities in the scanning process.
Q: How can this flaw be addressed?
A: The flaw can be addressed by implementing robust security measures in Nuclei’s template verification process, including ensuring the integrity and authenticity of templates.
