Summary
Nuclei: Environment Variable Disclosure via Response-Derived Data in DAST/Fuzz Mode
A vulnerability in Nuclei's DAST/fuzz expression evaluation path allows a malicious target server to trigger disclosure of scanner-host environment variables when the -env-vars / -ev option is explicitly enabled.
This is an incomplete fix for CVE-2026-41645 / GHSA-jm34-66cf-qpvr. The original fix hardened expressions.Evaluate() to be single-pass within one call, but did not address callers that invoked evaluation multiple times on substituted output in the DAST/fuzz pipeline.
Affected Component
The issue is in the DAST/fuzz payload evaluation path (pkg/fuzz/parts.go) and the shared template rendering boundary. When a multi-step template captures response data via an internal extractor and reuses it in a subsequent fuzz step, the fuzz evaluator could treat the substituted response content as fresh template syntax on a second evaluation pass.
Description
In DAST/fuzz mode, payload evaluation previously ran expression substitution more than once on the same value. Response-derived content captured by an internal: true extractor in a prior protocol step could flow into a fuzz payload and be reinterpreted as DSL/helper syntax on a subsequent pass.
When -env-vars (-ev) is enabled, environment variables are merged into the template variable map. A malicious target can return response data containing expressions like {{env_var_name}} which, when reused in a subsequent fuzz step, resolve to actual environment variable values. This can expose sensitive host data such as API keys, credentials, and tokens.
Without -ev enabled (the default), response-derived data may still cause other DSL helpers to run, but that behavior is not treated as a security issue and has no meaningful security impact beyond unexpected behavior.
[!NOTE]
The -env-vars / -ev option is off by default. Users who have not explicitly enabled it are not affected by this vulnerability.
Affected Users
- CLI users running
nuclei -dast(or fuzzing) with multi-step templates that chain an internal extractor into a subsequent fuzz step against untrusted targets, with the-evflag enabled. - SDK users who integrate Nuclei with the fuzz pipeline enabled,
EnvironmentVariablesset totrue, and scan targets that are not fully trusted.
Patches
- The vulnerability is fixed in Nuclei v3.10.0. Upgrading is strongly recommended.
- Fix reference: https://github.com/projectdiscovery/nuclei/pull/7499
- Related original fix: https://github.com/projectdiscovery/nuclei/pull/7221, https://github.com/projectdiscovery/nuclei/pull/7321
Mitigation
Upgrade to Nuclei v3.10.0, where template-authored text is rendered once through a shared rendering boundary and runtime values from responses, extractors, and constants remain opaque data.
If you have -ev enabled, disable it when scanning untrusted targets to avoid environment variable disclosure.
Workarounds
If upgrading is not an option, ensure -env-vars / -ev is not enabled when running DAST/fuzz scans with multi-step templates against untrusted targets.
Acknowledgments
Thanks to @BerSecHub for reporting this issue.
Impact
CVE-2026-76805 has a CVSS score of 5.3 (Medium). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (3.10.0); upgrading removes the vulnerable code path.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Already deployed Kodem?
See it in your environmentNew to Kodem? Get a demo →Remediation advice
Kodem Kai can prioritize this vulnerability in your dependency tree and generate a fix recommendation.
Frequently Asked Questions
- What is CVE-2026-76805? CVE-2026-76805 is a medium-severity security vulnerability in github.com/projectdiscovery/nuclei/v3 (go), affecting versions >= 3.0.0, < 3.10.0. It is fixed in 3.10.0.
- How severe is CVE-2026-76805? CVE-2026-76805 has a CVSS score of 5.3 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
- Which versions of github.com/projectdiscovery/nuclei/v3 are affected by CVE-2026-76805? github.com/projectdiscovery/nuclei/v3 (go) versions >= 3.0.0, < 3.10.0 is affected.
- Is there a fix for CVE-2026-76805? Yes. CVE-2026-76805 is fixed in 3.10.0. Upgrade to this version or later.
- Is CVE-2026-76805 exploitable, and should I be worried? Whether CVE-2026-76805 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-76805 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-76805? Upgrade
github.com/projectdiscovery/nuclei/v3to 3.10.0 or later.