CVE-2026-53540: Fastapiexpert Python-Multipart

Low severity, CVSS 3.7. EPSS: 0.3% chance of exploitation in the next 30 days.

Python-Multipart is a streaming multipart parser for Python. Prior to 0.0.31, parse_form() did not validate the Content-Length header before using it to bound its chunked read of the request body. A negative Content-Length turned the bounded read into a read-until-EOF, so the entire body was loaded into memory in a single read instead of in fixed-size chunks. This vulnerability is fixed in 0.0.31.

Affected products

• Fastapiexpert Python-Multipart: before 0.0.31 (fixed in 0.0.31)

Published 2026-06-22. Last modified 2026-06-26.