CVE-2026-53540

LOW

Python-Multipart: Negative Content-Length in parse_form buffers the entire body in memory

Title source: cna
STIX 2.1

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.

References (1)

Core 1
Core References

Scores

CVSS v3 3.7
EPSS 0.0022
EPSS Percentile 12.3%
Attack Vector NETWORK
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L

CISA SSVC

Vulnrichment
Exploitation none
Automatable no
Technical Impact partial

Details

CWE
CWE-1284
Status published
Products (2)
fastapiexpert/python-multipart < 0.0.31
Kludex/python-multipart < 0.0.31
Published Jun 22, 2026
Tracked Since Jun 22, 2026