Python: detecting header splitting in synthetic app #20919
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yoff
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yoff
November 26, 2025 12:39
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Pull request overview
This PR adds test coverage and modeling for header injection vulnerabilities using Python's http.server module and extends support for urllib.parse.ParseResult.
Key changes:
- Adds a test case demonstrating header injection vulnerability in
http.server.BaseHTTPRequestHandler - Introduces models for
urllib.parse.ParseResultclass to track taint propagation through URL parsing - Extends
urllib.parse.urlparsefunction modeling with taint propagation
Reviewed changes
Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.
| File | Description |
|---|---|
python/ql/test/query-tests/Security/CWE-113-HeaderInjection/Tests1/http_test.py |
New test case demonstrating header injection vulnerability using http.server module |
python/ql/test/query-tests/Security/CWE-113-HeaderInjection/Tests1/HeaderInjection.expected |
Updated expected test results to include new test case findings (generated file) |
python/ql/lib/semmle/python/frameworks/Stdlib.qll |
Adds ParseResult module with taint tracking for urllib.parse.ParseResult class |
python/ql/lib/semmle/python/frameworks/Stdlib.model.yml |
Adds taint model for urlparse function and type model for ParseResult class |
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| # if __name__ == "__main__": | ||
| # print("Serving vulnerable app on http://127.0.0.1:8080") | ||
| # httpd = HTTPServer(("127.0.0.1", 8080), VulnerableHandler) | ||
| # httpd.serve_forever() |
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Suggested change
| # if __name__ == "__main__": | |
| # print("Serving vulnerable app on http://127.0.0.1:8080") | |
| # httpd = HTTPServer(("127.0.0.1", 8080), VulnerableHandler) | |
| # httpd.serve_forever() | |
| # To run this server manually for testing, use: | |
| # python -m http.server 8080 --bind 127.0.0.1 | |
| # Or implement the main block as shown in documentation. |
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We normally leave such a code block there, so people can easily test for actual vulnerabilities.
| @@ -0,0 +1,22 @@ | |||
| from http.server import HTTPServer, BaseHTTPRequestHandler | |||
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Import of 'HTTPServer' is not used.
Suggested change
| from http.server import HTTPServer, BaseHTTPRequestHandler | |
| from http.server import BaseHTTPRequestHandler |
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Follow up work for https://github.com/github/field-security-codeql/issues/194