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.
Attack Parameters
Attack Vector
Network
Can be exploited remotely
Attack Complexity
Low
Easy to exploit
Attack Requirements
Present
Additional conditions required
Privileges Required
None
No privileges needed
User Interaction
Passive
Minimal interaction
Impact Assessment
Confidentiality
None
No data leak
Integrity
High
Complete data modification
Availability
None
No disruption
CVSS Vector v4.0
Weakness Type (CWE)
Vulnerable Products
python software foundation:cpython
References 10
https://github.com/python/cpython/issues/155292
cna@python.org
https://github.com/python/cpython/pull/155293
cna@python.org
https://mail.python.org/archives/list/security-announce@python.org/thread/EUHHT…
cna@python.org
http://www.openwall.com/lists/oss-security/2026/08/18/2
af854a3a-2127-422b-91ae-364da2661108
https://github.com/python/cpython/commit/7e109d084d55e7eb25837a5f3b47ef9beee547…
cna@python.org
https://github.com/python/cpython/commit/5181304bcec9cfc3c15311741c9154cdff2e3f…
cna@python.org
https://github.com/python/cpython/commit/1e54caa096678a38afcabecabb1ff72400dd6b…
cna@python.org
https://github.com/python/cpython/commit/c016c2535b74227fddf2cf7334dbfead6c9302…
cna@python.org
https://github.com/python/cpython/commit/c28b121a4f0b975937c8b5a1b4934bb361d842…
cna@python.org
https://github.com/python/cpython/commit/c42790b34f634051750e5da340d17c7da19e47…
cna@python.org