Nuclei: Environment Variable Disclosure via Response-Derived Data in DAST/Fuzz Mode

Summary

Nuclei is a vulnerability scanner built on a simple YAML-based DSL. From 3.0.0 until 3.10.0, the DAST/fuzz payload path in pkg/fuzz/parts.go can evaluate substituted runtime data more than once, creating a second evaluation pass that allows response content captured by an internal: true extractor in one protocol step to be reinterpreted as template syntax in a later fuzz step. This vulnerability is an incomplete fix for CVE-2026-41645: the prior remediation made expressions.Evaluate() single-pass within one call but did not prevent DAST/fuzz callers from evaluating substituted output again. When -env-vars is enabled, a malicious scan target can return marker-shaped content that resolves against the template variable map and discloses scanner-host environment variables such as credentials, API keys, or tokens. The vulnerability requires a multi-step DAST or fuzz template, response data reused through an internal extractor, and explicit environment-variable expansion; users who do not enable -env-vars are not affected by the sensitive-information disclosure. This issue is fixed in version 3.10.0.

Timeline

1. Sep 22, 2026, 4:48 PM UTCCVE published
2. Sep 22, 2026, 6:19 PM UTCCISA SSVC assessment

   Exploitation: none · Automatable: no · Technical impact: partial

3. Sep 22, 2026, 6:19 PM UTCRecord last updated

Affected versions

• projectdiscovery nuclei

  From 3.0.0 · fixed in 3.10.0

• github.com/projectdiscovery/nucleiGo

  All versions

• github.com/projectdiscovery/nuclei/v2Go

  All versions

• github.com/projectdiscovery/nuclei/v3Go

  From 3.0.0 · fixed in 3.10.0

References 4