CVE-2026-53539 (GCVE-0-2026-53539)

Vulnerability from cvelistv5 – Published: 2026-06-22 16:55 – Updated: 2026-06-23 16:08
VLAI
Title
Python-Multipart: Quadratic-time querystring parsing with semicolon separators causes CPU denial of service
Summary
Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.30, when parsing application/x-www-form-urlencoded bodies, QuerystringParser located the field separator with a two step lookup: it first scanned the entire remaining buffer for &, and only when no & existed anywhere ahead did it fall back to scanning for ;. For a body that uses ; as the separator and contains no &, every field iteration performed a full failed & scan over the entire remaining buffer before locating the nearby ;. With N semicolon separated fields in a chunk of size B, this yields O(B^2) byte comparisons per chunk. An attacker can submit a small crafted body of the form a;a;a;... and cause the parser to spend seconds of CPU per request. A handful of concurrent requests can exhaust worker processes. This vulnerability is fixed in 0.0.30.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-06-23 14:05 UTC
CWE
  • CWE-400 - Uncontrolled Resource Consumption
  • CWE-407 - Inefficient Algorithmic Complexity
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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