CVE-2026-53538 (GCVE-0-2026-53538)

Vulnerability from cvelistv5 – Published: 2026-06-22 16:56 – Updated: 2026-06-23 16:08
VLAI
Title
Python-Multipart: Semicolon treated as querystring field separator enables parameter smuggling
Summary
Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, QuerystringParser treated ; as a field separator in application/x-www-form-urlencoded bodies, in addition to &. The WHATWG URL standard, modern browsers, and Python's urllib.parse (since the CVE-2021-23336 fix) treat only & as a separator. This creates a parser differential: the same bytes are tokenized into different fields than a WHATWG compliant intermediary would produce, allowing an attacker to smuggle extra form fields past an upstream body inspecting component. This vulnerability is fixed in 0.0.30.
Severity
3.7 (Low)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-23 14:49 UTC
CWE
  • CWE-436 - Interpretation Conflict
  • CWE-444 - Inconsistent Interpretation of HTTP Requests ('HTTP Request/Response Smuggling')
Assigner
GitHub_M CNA under the mitre root
CNA scorecard C 72/100 over 7867 records in the last 180 days details
References
Impacted products
Vendor Product Version CPE status
Kludex python-multipart Affected: < 0.0.30
guessed Create a notification for this product.
Show details on NVD website
To clipboard 

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