Python Stringprep B.2/B.3 Unicode 3.2 Mismatch <3.15 Affected (Idna 2003)
CVE-2026-17084 Published on August 18, 2026
stringprep.map_table_b2() deviates from RFC 3454 Table B.2
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.
Vulnerability Analysis
CVE-2026-17084 is exploitable with network access. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have no impact on confidentiality and integrity and availability.
Weakness Type
Interpretation Conflict
Product A handles inputs or steps differently than Product B, which causes A to perform incorrect actions based on its perception of B's state. This is generally found in proxies, firewalls, anti-virus software, and other intermediary devices that monitor, allow, deny, or modify traffic based on how the client or server is expected to behave.
Products Associated with CVE-2026-17084
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Affected Versions
Python Software Foundation CPython:- Before 3.15.0 is affected.