Field Separator Handling Issue in Python-Multipart by Kludex
CVE-2026-53538

3.7LOW

Key Information:

Vendor

Kludex

Status
Python-multipart
Vendor
CVE Published:
22 June 2026

What is CVE-2026-53538?

The Python-Multipart library, used for streaming multipart parsing in Python, has a vulnerability where the QuerystringParser improperly treats ';' as a field separator in application/x-www-form-urlencoded data. This deviates from the expected behavior established by the WHATWG URL standard and impacts the security of data handling. This discrepancy allows attackers to potentially smuggle additional form fields past security checks of components that inspect the request body. This issue is resolved in version 0.0.30 of the library.

Affected Version(s)

python-multipart < 0.0.30

References

https://github.com/Kludex/python-multipart/security/advis...
x_refsource_CONFIRM

CVSS V3.1

Score:
3.7
Severity:
LOW
Confidentiality:
None
Integrity:
Low
Availability:
None
Attack Vector:
Network
Attack Complexity:
High
Privileges Required:
None
User Interaction:
None
Scope:
Unchanged

Timeline

  • Vulnerability published

  • Vulnerability Reserved

.