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: <validsignatureforbenigncontent> digest: <anothersignature>\r code:\r - engine:\r - sh\r - bash\r source: |\r id\r Patches 1. The vulnerability is addressed in Nuclei v3.3.2 Users are strongly recommended to update to this version to mitigate the security risk. 2. Fix reference - https://github.com/projectdiscovery/nuclei/commit/0da993afe6d41b4b1b814e8fad23a2acba13c60a
Mitigation - Immediate Upgrade: The primary recommendation is to upgrade to Nuclei v3.2.0, where the vulnerability has been patched. - Avoid Unverified Templates: As an interim measure, users should refrain from using custom templates if unable to upgrade immediately. Only trusted, verified templates should be executed.
Workarounds If you are unable to upgrade nuclei, disable running custom code templates as workaround.
Acknowledgments
We would like to thank Guy Goldenberg from Wiz who reported this to us via our security email, security@projectdiscovery.io.
Overview
We have identified and addressed a security issue in the Nuclei project that affected users utilizing Nuclei as Go code (SDK) running custom templates. This issue did not affect CLI users. The problem was related to sanitization issues with payloads loading in sandbox mode.
Details
In the previous versions, there was a potential risk with payloads loading in sandbox mode. The issue occurred due to relative paths not being converted to absolute paths before doing the check for sandbox flag allowing arbitrary files to be read on the filesystem in certain cases when using Nuclei from Go SDK implementation.
This issue has been fixed in the latest release, v2.9.9. We have also enabled sandbox by default for filesystem loading. This can be optionally disabled if required.
The -sandbox option has been deprecated and is now divided into two new options: -lfa (allow local file access) which is disabled by default and -lna (restrict local network access) which can be optionally disabled by user. The -lfa allows file (payload) access anywhere on the system (disabling sandbox effectively), and -lna blocks connections to the local/private network.
Affected Versions
This issue affected all versions of Nuclei prior to v2.9.9.
Patches
We recommend all users upgrade to the latest version, v2.9.9, which includes the security fix.
References
- patch - releases
Acknowledgments
We would like to thank keomutchoiboi who reported this issue to us via our security email, security@projectdiscovery.io. We appreciate the responsible disclosure of this issue.