abirasecurity/CVE-2021-21974_vuln_dectection

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PoC files

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GitHub
Analysisdeepseek-v4-pro:cloud ·

Technical assessment

A Python-based scanner that checks for the CVE-2021-21974 vulnerability in VMware ESXi SLP services by probing service availability, fingerprinting the implementation, and testing boundary/malformed packet handling without performing exploitation.

Backdoor review

No backdoor observed in reviewed code

The artifact is a Python script and README that perform safe, non-exploitative detection of CVE-2021-21974. The code sends crafted SLP packets to a user-supplied target to fingerprint the service and test boundary/malformed packet handling, but it does not execute any payload, establish persistence, exfiltrate data, or contact any attacker-controlled infrastructure. No concealed or deceptive behavior was found.

ClassificationScanner
Model confidence98%
AuthenticationNot required
Languagespython
Target softwareVMware ESXiOpenSLP
Attack typesvulnerability scanning
Evidence & reasoningClassification basis · observed behavior · safety review
Technical evidence

Classification basis and observed behavior

Classification basis

The artifact is a scanner because it only detects, validates, and reports exposure to CVE-2021-21974 without exploiting the vulnerability. The code explicitly states it is a 'Safe PoC that identifies vulnerable SLP implementations without exploitation' and performs non-destructive checks like service probing, fingerprinting, and boundary testing.

CVE-2021-21974_detector.py:3-4README.md:3README.md:15

Requirements

  • Network access to target on port 427CVE-2021-21974_detector.py:14-16
  • Python 3.x with standard librariesREADME.md:29-35

Observed behavior

  • Connects to target on port 427 and sends a basic SLP service request to check availabilityCVE-2021-21974_detector.py:68-91
  • Sends SLP Directory Agent Advertisement packets with varying URL and scope lengths to test boundary conditionsCVE-2021-21974_detector.py:93-133
  • Sends malformed SLP packets to evaluate error handlingCVE-2021-21974_detector.py:135-158
  • Fingerprints SLP implementation by analyzing response version and function IDCVE-2021-21974_detector.py:160-192
  • Assesses vulnerability likelihood based on detected implementation and reports resultsCVE-2021-21974_detector.py:194-247
Safety-review evidence

Behaviors behind the backdoor verdict

Observables

Network Connection
TCP connection to user-supplied target IP on port 427The script connects to the target specified by the user to perform vulnerability detection. This is expected behavior for a PoC scanner and is not a backdoor.CVE-2021-21974_detector.py:14-16CVE-2021-21974_detector.py:71-73
User Input
Command-line argument <target_ip>The script takes a target IP address as a command-line argument. No hidden or hardcoded targets are present.CVE-2021-21974_detector.py:250-254
Review boundaries

What the analysis did not establish

  • Review is limited to the supplied text files (CVE-2021-21974_detector.py and README.md). No binary files were present or analyzed.
  • The script's behavior depends on the target's response; the review does not assess the safety of running the script against a malicious target that could exploit the scanner itself, though no such vulnerability is apparent in the code.
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