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CVE-2026-17084

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

MEDIUM
6
CVSS Score
Published: August 18, 2026 at 01:57 PM UTC
Updated: October 22, 2026 at 10:10 PM UTC
1 product affected across 1 vendorPython

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Severity
MEDIUM6
Exploit prediction
EPSS 0.7%
SSVC
No known exploit

Description

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Python· Python
90%
0 ≤ v < 3.10.223.11.0 ≤ v < 3.11.173.12.0 ≤ v < 3.12.153.13.0 ≤ v < 3.13.163.14.0 ≤ v < 3.14.83.15.0a1 ≤ v < 3.15.0rc203.11.03.12.03.13.03.14.03.15.0a1
Affected range stops below 3.10.22, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.11.17, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.12.15, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.13.16, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.14.8, so it looks safe — our inference, not a vendor statement
Affected range stops below 3.15.0rc2, so it looks safe — our inference, not a vendor statement

References (12)

Patch
Source: cverecord
https://github.com/python/cpython/pull/155293
Issue Tracking
Source: cverecord
https://github.com/python/cpython/issues/155292
Vendor Advisory
Source: cverecord
https://mail.python.org/archives/list/[email protected]/thread/EUHHTC6EV7HCLSUHP25C5VHSV4V2MUZN/
Source: af854a3a-2127-422b-91ae-364da2661108
http://www.openwall.com/lists/oss-security/2026/08/18/2
Patch
Source: cverecord
https://github.com/python/cpython/commit/7e109d084d55e7eb25837a5f3b47ef9beee547bc
Patch
Source: cverecord
https://github.com/python/cpython/commit/5181304bcec9cfc3c15311741c9154cdff2e3fd7
Patch
Source: cverecord
https://github.com/python/cpython/commit/1e54caa096678a38afcabecabb1ff72400dd6bae
Patch
Source: cverecord
https://github.com/python/cpython/commit/c016c2535b74227fddf2cf7334dbfead6c930214

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

6MEDIUMPSF
Vector?

Quick Info

StatusAWAITING ANALYSIS
CWE
CWE-436

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