0xCyberstan/CVE-2026-42533-Config-Scanner

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PoC files

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GitHub
Analysisdeepseek-v4-pro:cloud ·

Technical assessment

A Python-based static analysis scanner that parses nginx configuration files to detect patterns vulnerable to CVE-2026-42533, a heap buffer overflow in the complex_value two-pass capture-clobbering bug class. It does not exploit the vulnerability; it only reads config files and reports findings.

Backdoor review

No backdoor observed in reviewed code

The repository contains a static analysis scanner for the CVE-2026-42533 nginx vulnerability. The Python script and README describe and implement a read-only config parser that flags vulnerable patterns. No backdoor, deceptive payload, or concealed harmful behavior is present in the reviewed text.

ClassificationScanner
Model confidence100%
AuthenticationNot required
LanguagesPython
Target softwareNGINX PlusNGINX Open Source
Attack typesheap buffer overflowinformation disclosure
Evidence & reasoningClassification basis · observed behavior · safety review
Technical evidence

Classification basis and observed behavior

Classification basis

The artifact is a read-only static analysis tool that parses nginx configuration files to detect vulnerable patterns. It does not contain any code to send crafted HTTP requests, trigger the buffer overflow, or execute a payload. The README explicitly states it 'does not exploit anything and does not touch the running server' and the code only performs file I/O and analysis.

README.md:3-7nginx_capture_clobber_scan.py:2-9

Requirements

  • Read access to nginx configuration files on the local filesystem.nginx_capture_clobber_scan.py:110-111
  • Python 3.6+ with standard library only.README.md:9

Observed behavior

  • Parses nginx configuration files, including following 'include' directives, to identify locations where a regex capture variable and a regex map variable share a two-pass buffer in an exploitable order.nginx_capture_clobber_scan.py:307-375README.md:35-52
  • Outputs a report (text or JSON) listing vulnerable configurations, cleared (safe but fragile) configurations, and any unreadable include files. Exits with code 1 if vulnerabilities are found, 0 otherwise.nginx_capture_clobber_scan.py:443-515README.md:80-92
  • Does not send any network requests, does not interact with a running nginx server, and does not attempt to trigger the vulnerability.README.md:3-7nginx_capture_clobber_scan.py:2-9
Safety-review evidence

Behaviors behind the backdoor verdict

Observables

Url
https://cyberstan.co.uk/nginx-rce/External reference to a vulnerability write-up and exploit chain, mentioned in README and script docstring. The URL itself is not executed by the artifact.README.md:12README.md:147
Review boundaries

What the analysis did not establish

  • The evidence packet reports complete_artifact_coverage as false, indicating that not all files in the repository were included. Only two text files (README.md and nginx_capture_clobber_scan.py) are provided, and the analysis scope notes TEXT_EXCEEDS_ONE_CALL_BUDGET. Other files, if any exist in the repository, were not inspected.
  • Only the two text files (README.md and nginx_capture_clobber_scan.py) were provided and reviewed. No binary files were present. The review does not verify the correctness or safety of the external URL https://cyberstan.co.uk/nginx-rce/.
Model interpretation

This review is limited to the supplied PoC code and context. It does not assert that the code works or is safe to execute.

Linked vulnerabilities

1