Nuclei Template Signature Verification Bypass
Date: 2024-09
Affected: go/github.com/projectdiscovery/nuclei/v3
Attack vector: command-injection
Category: vulnerability-disclosure
Severity: Medium
CVE: CVE-2024-43405
CWE: CWE-78
CVSS: 7.4 (CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:C/C:H/I:H/A:N)

## Summary A vulnerability has been identified in Nuclei's template signature verification system that could allow an attacker to bypass the signature check and possibly execute malicious code via custom code template. ## Affected Component The vulnerability is present in the template signature verification process, specifically in the `signer` package. ## Description The vulnerability stems from a discrepancy between how the signature verification process and the YAML parser handle newline characters, combined with the way multiple signatures are processed. This allows an attacker to inject malicious content into a template while maintaining a valid signature for the benign part of the template. ### Affected Users 1. **CLI Users:** Those executing **custom code templates** from unverified sources. This includes templates authored by third parties or obtained from unverified repositories. 2. **SDK Users:** Developers integrating Nuclei into their platforms, particularly if they permit the execution of **custom code templates** by end-users. > [!NOTE] > Code templates are disabled as default, users have to explicitly enable with `-code` option. ## Proof of Concept ```yaml id: example-template info: name: Example Template # Other benign content... # digest: <valid_signature_for_benign_content> # digest: <another_signature>\r code:\r - engine:\r - sh\r - bash\r source: |\r id\r ``` ### Patches 1. The vulnerability is addressed in Nuclei v3.3.2 Us


Mitigations:

Architectural layers (MAESTRO):