CVEvulnerability

CVE-2026-53538

3.7 LOW Published 2026-06-22 Modified 2026-10-25 Official page ↗
Status
Analyzed
Published
2026-06-22
Last modified
2026-10-25
Assigner
[email protected]
CVSS 3.1 ([email protected])
3.7 LOW — CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:L/A:N
Weaknesses
CWE-436, CWE-444

Description

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.

Affected configurations

• fastapiexpert python-multipart (< 0.0.30)

Related

Weakness · CWE (2)

  • CWE-436 Interpretation Conflict weakness
  • CWE-444 Inconsistent Interpretation of HTTP Requests weakness

References