CVE-2026-17084

UNKNOWN 0.0

stringprep.map_table_b2() deviates from RFC 3454 Table B.2

CVSS Score

0.0

EPSS Score

0.0%

EPSS Percentile

0th

The "stringprep" module didn't process characters from RFC 3454 tables B.2 or B.3 correctly: the latest Unicode codepoint attributes were used instead of the specified Unicode 3.2.0. This behavior would cause mismatches when processing domain names using IDNA 2003 (the "idna" codec) and the in_table_b2() function of the "stringprep" module. This only affects domain names containing characters that were not previously registered or had their Unicode attributes such as case-folding behavior updated since Unicode 3.2.0.

Vendor	python software foundation
Product	cpython
Published	Aug 18, 2026
Last Updated	Aug 18, 2026

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Affected Versions

Python Software Foundation / CPython

0 < 3.16.0

References

NVD ↗ CVE.org ↗ EPSS Data ↗

github.com: https://github.com/python/cpython/pull/155293 github.com: https://github.com/python/cpython/issues/155292 mail.python.org: https://mail.python.org/archives/list/[email protected]/thread/EUHHTC6EV7HCLSUHP25C5VHSV4V2MUZN/

Credits

🔍 Bitshift (https://github.com/TheShiftedBit) Seth Larson (https://github.com/sethmlarson) Stan Ulbrych (https://github.com/StanFromIreland) Marc-Andre Lemburg (https://github.com/malemburg) Petr Viktorin (https://github.com/encukou)