Low severity · published Jun 22, 2026
CVE-2026-53540
Python-Multipart: Negative Content-Length in parse_form buffers the entire body in memory
3.7
CVSS
0.3%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
High
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 28% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
PY
python-multipart · Kludex
< 0.0.31 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-53540
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-53540
Vendor Advisory
https://github.com/Kludex/python-multipart/security/advisories/GHSA-v9pg-7xvm-68hf
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