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CVE-2026-17084PATCHED
Python Software Foundation · CPython

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

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 Products

VendorProductVersions
Python Software FoundationCPython0, 3.11.0, 3.12.0, 3.13.0, 3.14.0, 3.15.0a1

Also Affects

Downstream vendors/products affected by this vulnerability

VendorProductSourceConfidence
open sourcepythoncert_advisory90%

References

  • https://github.com/python/cpython/pull/155293(patch)
  • https://github.com/python/cpython/issues/155292(issue-tracking)
  • https://mail.python.org/archives/list/security-announce@python.org/thread/EUHHTC6EV7HCLSUHP25C5VHSV4V2MUZN/(vendor-advisory)
  • https://github.com/python/cpython/commit/7e109d084d55e7eb25837a5f3b47ef9beee547bc(patch)
  • https://github.com/python/cpython/commit/5181304bcec9cfc3c15311741c9154cdff2e3fd7(patch)
  • https://github.com/python/cpython/commit/1e54caa096678a38afcabecabb1ff72400dd6bae(patch)
  • https://github.com/python/cpython/commit/c016c2535b74227fddf2cf7334dbfead6c930214(patch)
  • https://github.com/python/cpython/commit/c28b121a4f0b975937c8b5a1b4934bb361d84296(patch)
  • https://github.com/python/cpython/commit/c42790b34f634051750e5da340d17c7da19e4784(patch)
  • https://github.com/python/cpython/commit/69f92ebaec681e9149dfd70fd02d4ed52d2a6296(patch)
  • https://github.com/python/cpython/commit/d397a4979cfc80a8cd6c73838aa10e9c8cf5ef72(patch)

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CPython [CVE-2026-17084] StringPrep algorithm considered Unicode codepoint attributes outside Unicode 3.2.0
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CVE-2026-17084 | Python up to 3.15.x stringprep in_table_b2 input validation
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Discussion (0)

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CISA KEV❌ No
Actively exploited❌ No
Patch available
3.16.0
PublishedAug 18, 2026
Last enriched62d ago
Trending Score5
Source articles6
Independent5
Info Completeness7/14
Missing: cvss, epss, cwe, kev, exploit, iocs, mitre_attack

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Verification

State: verified
Confidence: 0%

Vulnerability Timeline

CVE Published
Aug 18, 2026
Discovered by ZDM
Aug 18, 2026
Patch Available
Oct 2, 2026