Low [CVE-2026-53540] Negative Content-Length in parse_form buffers the entire body in memory
This low-severity Red Hat Linux advisory covers CVE-2026-53540 affecting Exploit Intelligence, Migration Toolkit for Applications 8, OpenShift Lightspeed.
Aggregated and source-linked by VulniPulse. Data sources, validation and limitations.
VulniPulse record published Record updated
Summary
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. The realistic exposure is limited to bespoke WSGI or http.server handlers that forward raw client headers directly into parse_form().
Common frameworks such as Starlette and FastAPI do not call parse_form() directly and are not affected by this specific code path. Red Hat severity: Low — CVSS 3.7 (CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:L).
Weakness: CWE-400. Affected Red Hat products: Exploit Intelligence; Migration Toolkit for Applications 8; OpenShift Lightspeed; Red Hat AI Inference Server; Red Hat Ansible Automation Platform 2; Red Hat Enterprise Linux AI (RHEL AI) 3; Red Hat OpenShift AI (RHOAI); Red Hat OpenShift Virtualization 4; Red Hat Satellite 6.
Red Hat lists OpenShift Lightspeed; Red Hat Hardened Images as not affected. Red Hat does not currently list a fixing RHSA for this CVE.
Is CVE-2026-53540 exploited?
No exploitation is reported in the sources VulniPulse tracks: CVE-2026-53540 is not in the CISA KEV catalog (checked ) and this advisory does not report exploitation. That is not proof the vulnerability cannot be exploited.
How do I fix CVE-2026-53540?
Upgrade to a fixed release named by Red Hat:
- 0.0.31
Confirm against the vendor advisory before you patch.
- < 0.0.31
Official advisory · high-confidence parse· fetched 14 days ago·verify at source
Mitigation checklist
- Upgrade python-multipart to version 0.0.31 or later, which rejects a negative Content-Length with a ValueError before reading the stream. As a workaround, configure the HTTP stack or reverse proxy to reject or normalize negative Content-Length headers before they reach the application layer.
Official advisory · high-confidence parse· fetched 14 days ago·verify at source
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