{
  "affected": [
    {
      "package": {
        "ecosystem": "Go",
        "name": "github.com/projectdiscovery/nuclei/v3"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "3.0.0"
            },
            {
              "fixed": "3.8.0"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "aliases": [
    "CVE-2026-41645"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-94"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-04-22T19:59:14Z",
    "nvd_published_at": null,
    "severity": "MODERATE"
  },
  "details": "A vulnerability in Nuclei\u0027s expression evaluation engine makes it possible for a malicious target server to inject and execute supported DSL expressions. This happens when HTTP response data containing helper/function syntax gets reused by multi-step templates. If the `-env-vars` / `-ev` option is explicitly enabled, this can expose host environment variables. That option is off by default, so standard configurations are not affected by the information disclosure risk.\n\n**Affected Component**\n\nThe issue lives in `expressions.Evaluate()` at `pkg/protocols/common/expressions/` and in the unresolved-variable validation path (`hasLiteralsOnly()`).\n\n**Description**\n\n`expressions.Evaluate()` replaces placeholders first, then scans the substituted output for expressions. Because of this two-pass approach, response-derived values (including extractor output and response body content) can be reinterpreted as DSL/helper syntax on the second pass.\n\nWhen `-env-vars` (`-ev`) is enabled, environment variables get 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 template request, resolve to actual environment variable values. This can expose sensitive host data like API keys, credentials, and tokens.\n\nWithout `-ev` enabled (the default), injected DSL expressions may still trigger helper functions such as `{{md5(\"test\")}}`, but this has no meaningful security impact beyond unexpected behavior.\n\nThere is also a separate issue in `hasLiteralsOnly()`: it was evaluating helper expressions while deciding whether `{{...}}` contained unresolved variables, which caused validation logic to run side-effectful helpers even when the final request kept the value as a literal.\n\n\u003e [!NOTE]\nThe `-env-vars` / `-ev` option is off by default. Users who have not explicitly turned it on are not affected by the information disclosure aspect of this vulnerability.\n\n**Affected Users**\n\n- **CLI users** running multi-step templates (with extractors or flow-based request chaining) that reuse response-derived values against untrusted or attacker-controlled targets, with the `-ev` flag enabled.\n- **SDK users** who have integrated Nuclei into platforms where `EnvironmentVariables` is set to `true` and scan targets are not fully trusted.\n\n**Patches**\n\n- The vulnerability is fixed in Nuclei v3.8.0. Upgrading to this version is strongly recommended.\n- Relevant fix references: #7221, #7321.\n\n**Mitigation**\n\nUpgrade to Nuclei v3.8.0. The updated evaluation logic now collects expressions from the original template text before placeholder substitution and only evaluates those template-authored expressions.\n\nIf you have `-ev` enabled, disable it when scanning untrusted targets to avoid environment variable disclosure.\n\n**Workarounds**\n\nIf upgrading is not an option right now, make sure `-env-vars` / `-ev` is not enabled when running multi-step templates against untrusted targets.\n\n**Acknowledgments**\n\nNuclei thanks @gnuletik for reporting this issue through responsible disclosure via security@projectdiscovery.io",
  "id": "GHSA-jm34-66cf-qpvr",
  "modified": "2026-04-22T19:59:14Z",
  "published": "2026-04-22T19:59:14Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/projectdiscovery/nuclei/security/advisories/GHSA-jm34-66cf-qpvr"
    },
    {
      "type": "WEB",
      "url": "https://github.com/projectdiscovery/nuclei/pull/7221"
    },
    {
      "type": "WEB",
      "url": "https://github.com/projectdiscovery/nuclei/pull/7321"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/projectdiscovery/nuclei"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:N/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "Nuclei: Environment variable disclosure via Response-Derived DSL Expressions"
}