CVE-2026-17084
stringprep.map_table_b2() deviates from RFC 3454 Table B.2
CVSS Score
0.0
EPSS Score
0.7%
EPSS Percentile
52th
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 | Oct 2, 2026 |
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Affected Versions
Python Software Foundation / CPython
0 < 3.10.22 3.11.0 < 3.11.17 3.12.0 < 3.12.15 3.13.0 < 3.13.16 3.14.0 < 3.14.8 3.15.0a1 < 3.15.0rc2
References
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/ github.com: https://github.com/python/cpython/commit/7e109d084d55e7eb25837a5f3b47ef9beee547bc github.com: https://github.com/python/cpython/commit/5181304bcec9cfc3c15311741c9154cdff2e3fd7 github.com: https://github.com/python/cpython/commit/1e54caa096678a38afcabecabb1ff72400dd6bae github.com: https://github.com/python/cpython/commit/c016c2535b74227fddf2cf7334dbfead6c930214 github.com: https://github.com/python/cpython/commit/c28b121a4f0b975937c8b5a1b4934bb361d84296 github.com: https://github.com/python/cpython/commit/c42790b34f634051750e5da340d17c7da19e4784 github.com: https://github.com/python/cpython/commit/69f92ebaec681e9149dfd70fd02d4ed52d2a6296 github.com: https://github.com/python/cpython/commit/d397a4979cfc80a8cd6c73838aa10e9c8cf5ef72 openwall.com: http://www.openwall.com/lists/oss-security/2026/08/18/2
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)