Summary
Nuclei: Local File Read via MySQL Client Sandbox Bypass
A vulnerability in Nuclei's JavaScript MySQL client library allows arbitrary local file reads that bypass the -allow-local-file-access (-lfa) sandbox restriction.
Affected Component
The issue is in the nuclei/mysql JavaScript library used by javascript: protocol templates. The MySQL client connection logic did not enforce the local file access sandbox when handling the allowAllFiles DSN parameter used by LOAD DATA LOCAL INFILE.
Description
Without -lfa, Nuclei confines local file access to the templates directory. However, a javascript: template could connect to a MySQL server with allowAllFiles=true in the connection DSN. With this option enabled, a malicious MySQL server can issue LOAD DATA LOCAL INFILE requests for arbitrary paths on the scanner host. The MySQL client reads the full file contents and sends them to the server, bypassing the same sandbox that blocks direct filesystem reads through other APIs.
javascript: templates execute without the -code flag and unsigned javascript: templates run by default, making this reachable from untrusted third-party templates when scanning attacker-controlled MySQL endpoints.
[!NOTE]
The -allow-local-file-access (-lfa) option is off by default. This issue allows bypassing that restriction, not merely expanding an already-enabled capability.
Affected Users
- CLI users running untrusted or third-party
javascript:templates against MySQL-compatible targets. - SDK users who integrate Nuclei into platforms where end users can supply JavaScript templates and rely on the default
-lfarestriction to limit filesystem access.
Patches
- The vulnerability is fixed in Nuclei v3.10.0. Upgrading is strongly recommended.
- Fix reference: https://github.com/projectdiscovery/nuclei/pull/7473
Mitigation
Upgrade to Nuclei v3.10.0, where the allowAllFiles DSN option is stripped unless -lfa is explicitly enabled.
In the meantime, avoid running JavaScript templates from unverified sources, especially against untrusted database endpoints.
Workarounds
If upgrading is not an option, avoid running untrusted JavaScript templates. There is no flag or configuration that mitigates this bypass on affected versions.
Acknowledgments
Thanks to @daffainfo for reporting this issue.
Impact
CVE-2026-76803 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.
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Frequently Asked Questions
- What is CVE-2026-76803? CVE-2026-76803 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-2026-76803? CVE-2026-76803 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-2026-76803? github.com/projectdiscovery/nuclei/v3 (go) versions >= 3.0.0, < 3.10.0 is affected.
- Is there a fix for CVE-2026-76803? Yes. CVE-2026-76803 is fixed in 3.10.0. Upgrade to this version or later.
- Is CVE-2026-76803 exploitable, and should I be worried? Whether CVE-2026-76803 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-2026-76803 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-2026-76803? Upgrade
github.com/projectdiscovery/nuclei/v3to 3.10.0 or later.