CVE-2026-53540: fastapiexpert python-multipart

Vulnerability summary

CVE-2026-53540 is a low (CVSS 3.7) vulnerability in fastapiexpert python-multipart. EPSS estimates a 0.34% chance of exploitation in the next 30 days, higher than 26.2% of scored vulnerabilities.

Timeline

1. 22-06-2026
   PublishedVulnerability first disclosed.
2. 22-06-2026
   Last modifiedVulnerability information updated.

Description

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.

• CWE-1284Improper Validation of Specified Quantity in InputThe product receives input that is expected to specify a quantity (such as size or length), but it does not validate or incorrectly validates that the quantity has the required properties.