CVE-2026-17084: Vulnerability in Python Software Foundation CPython
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.
AI Analysis
Technical Summary
The stringprep module in CPython versions before 3.16.0 does not correctly process characters from RFC 3454 tables B.2 and B.3 because it uses the latest Unicode codepoint attributes instead of the specified Unicode 3.2.0 attributes. This causes mismatches in domain name processing using the IDNA 2003 codec and the in_table_b2() function, specifically for domain names containing characters whose Unicode attributes, such as case-folding behavior, have changed since Unicode 3.2.0.
Potential Impact
This vulnerability causes incorrect processing of domain names containing certain Unicode characters, potentially leading to mismatches or failures in domain name handling when using IDNA 2003. This could affect applications relying on CPython's stringprep module for domain name normalization or validation, possibly impacting domain name resolution or security checks involving internationalized domain names.
Mitigation Recommendations
Patch status is not yet confirmed — check the Python Software Foundation advisory for current remediation guidance. Until an official fix is released, users should be aware of the potential for domain name processing mismatches when using affected CPython versions with IDNA 2003.
CVE-2026-17084: Vulnerability in Python Software Foundation CPython
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.
CVSS v4.0
Score 6.0medium
Affected software
Run on your own infrastructure? Check whether these packages are installed with threat-finder — our free open-source scanner.
Weaknesses
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The stringprep module in CPython versions before 3.16.0 does not correctly process characters from RFC 3454 tables B.2 and B.3 because it uses the latest Unicode codepoint attributes instead of the specified Unicode 3.2.0 attributes. This causes mismatches in domain name processing using the IDNA 2003 codec and the in_table_b2() function, specifically for domain names containing characters whose Unicode attributes, such as case-folding behavior, have changed since Unicode 3.2.0.
Potential Impact
This vulnerability causes incorrect processing of domain names containing certain Unicode characters, potentially leading to mismatches or failures in domain name handling when using IDNA 2003. This could affect applications relying on CPython's stringprep module for domain name normalization or validation, possibly impacting domain name resolution or security checks involving internationalized domain names.
Mitigation Recommendations
Patch status is not yet confirmed — check the Python Software Foundation advisory for current remediation guidance. Until an official fix is released, users should be aware of the potential for domain name processing mismatches when using affected CPython versions with IDNA 2003.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- PSF
- Date Reserved
- 2026-07-24T14:36:15.943Z
- Cvss Version
- 4.0
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 6a846685c6e8be03324c8d47
Added to database: 08/18/2026, 14:04:53 UTC
Last enriched: 08/18/2026, 14:21:10 UTC
Last updated: 08/19/2026, 02:52:02 UTC
Views: 8
Community Reviews
0 reviewsCrowdsource mitigation strategies, share intel context, and vote on the most helpful responses. Sign in to add your voice and help keep defenders ahead.
Want to contribute mitigation steps or threat intel context? Sign in or create an account to join the community discussion.
Actions
Updates to AI analysis require Pro Console access. Upgrade inside Console → Billing.
Need more coverage?
Upgrade to Pro Console for AI refresh and higher limits.
For incident response and remediation, OffSeq services can help resolve threats faster.
Latest Threats
Check if your credentials are on the dark web
Instant breach scanning across billions of leaked records. Free tier available.