Nuclei: Arbitrary Command Execution via DAST Code Signature Bypass

A vulnerability in Nuclei's DAST template loading path allows unsigned code: protocol templates to execute, bypassing the cryptographic signature requirement that is meant to prevent arbitrary command execution from untrusted templates.

Affected Component

The issue is in the template loader's DAST loading branch. When -dast is enabled and a template contains a fuzzing: block, the loader accepted the template through a code path that omitted the unsigned-code-template signature check present in the normal loading branch.

Description

Nuclei requires code: protocol templates to be cryptographically signed before execution. Unsigned code templates are normally skipped with a warning. However, when a template combined a fuzzing: block (making it DAST-eligible) with an unsigned code: block, enabling -dast routed the template through the DAST loader branch, which did not enforce signature verification.

For multiprotocol templates containing both HTTP and code: blocks, the unsigned code request was included in the execution queue regardless of whether -code was set. This allowed arbitrary shell command execution from an unsigned code: block with only -dast enabled.

[!NOTE]
Both DAST mode (-dast) and code-protocol templates are disabled by default. Code templates normally require both the -code flag and a valid template signature. This issue bypassed the signature and -code controls only when -dast was explicitly enabled.

Affected Users

• CLI users running DAST/fuzzing scans (-dast) with untrusted or attacker-supplied templates that contain both fuzzing: and code: blocks.
• SDK users who integrate Nuclei with DAST mode enabled and allow end users to supply custom templates.

Patches

• The vulnerability is fixed in Nuclei v3.10.0. Upgrading is strongly recommended.
• Fix reference: https://github.com/projectdiscovery/nuclei/pull/7472

Mitigation

Upgrade to Nuclei v3.10.0, where code template signature verification is enforced before DAST loading.

In the meantime, avoid running DAST scans with untrusted templates.

Workarounds

If upgrading is not an option, do not use -dast with templates from unverified sources.

Acknowledgments

Thanks to @daffainfo for reporting this issue.