stringprep.map_table_b2() deviates from RFC 3454 Table B.2
13Vexday Risk Score
No sign of exploitation. No public exploitation artifact known so far.
ssvc Trackcvss 6epss 0.6%
exploitation probability
0.6%top 53% of all CVEs
observed exploitation
nono source reports it
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.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
Affected products
Python Software Foundation · CPythonReferences
https://github.com/python/cpython/commit/1e54caa096678a38afcabecabb1ff72400dd6baehttps://github.com/python/cpython/commit/5181304bcec9cfc3c15311741c9154cdff2e3fd7https://github.com/python/cpython/commit/7e109d084d55e7eb25837a5f3b47ef9beee547bchttps://github.com/python/cpython/commit/c016c2535b74227fddf2cf7334dbfead6c930214https://github.com/python/cpython/commit/c28b121a4f0b975937c8b5a1b4934bb361d84296https://github.com/python/cpython/commit/c42790b34f634051750e5da340d17c7da19e4784https://github.com/python/cpython/issues/155292https://github.com/python/cpython/pull/155293https://mail.python.org/archives/list/security-announce@python.org/thread/EUHHTC6EV7HCLSUHP25C5VHSV4V2MUZN/http://www.openwall.com/lists/oss-security/2026/08/18/2