gh-142533: Document CRLF injection vulnerability in http.server and wsgiref modules#143395
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tadejmagajna wants to merge 4 commits intopython:mainfrom
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gh-142533: Document CRLF injection vulnerability in http.server and wsgiref modules#143395tadejmagajna wants to merge 4 commits intopython:mainfrom
tadejmagajna wants to merge 4 commits intopython:mainfrom
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… and wsgiref modules
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Hi, according to the Dev Guide, the document only changes don't need a news entry file. |
picnixz
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Jan 4, 2026
Doc/library/http.server.rst
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| This method does not reject input containing CRLF sequences allowing the | ||
| possibility of CRLF injection, where a single method call can inject | ||
| multiple arbitrary headers. |
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Suggested change
| This method does not reject input containing CRLF sequences allowing the | |
| possibility of CRLF injection, where a single method call can inject | |
| multiple arbitrary headers. | |
| This method does not reject input containing CRLF sequences. |
Only mention the possibility of CRLF injection in the security consideration section.
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Thank you for the suggestion. Addressed for both modules
Doc/library/wsgiref.rst
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| This method does not reject input containing CRLF sequences allowing the | ||
| possibility of CRLF injection, where a single method call can inject | ||
| multiple arbitrary headers. |
picnixz
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Jan 4, 2026
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| Security considerations | ||
| ----------------------- |
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Please format this the same as we did for Http.server, that is: add a label and enough blank lines.
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@picnixz thank you for the suggestions. I believe this is addressed now. |
picnixz
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Jan 19, 2026
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cc @SethMichaelLarson @gpshead @serhiy-storchaka: Do you want to double check this change? |
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This change documents the CRLF injection vulnerability for http headers in
http.serverandwsgirefmodules.Initial report in #142533 focused on
http.serveronly, though further discussion suggested also addressing a closely related vulnerability inwsgirefreferenced in related issues #55880 and #72964.After discussing #142605, we pivoted from a direct fix to a documentation update because a fix would disrupt users who rely on using the vulnerability for non-malicious purposes.
The change documents the low-level vulnerability (i.e. absence of checking for CRLF) in mehod-specific sections while describing the high level implications (i.e. assuming sanitized input) under the "Security considerations" section.
http.server#142533📚 Documentation preview 📚: https://cpython-previews--143395.org.readthedocs.build/