High, CVSS 7.5PyPIAmendedPublished
multipart vulnerable to ReDoS in parse_options_header()
CVE-2026-28356 · GHSA-p2m9-wcp5-6qw3
- Affected
- PyPI multipart >= 1.3.0, < 1.3.1; < 1.2.2
- Fixed in
- 1.2.21.3.1· Vendor fix available
- Issue
- The parseoptionsheader() function in multipart.py uses a regular expression with an ambiguous alternation, which can cause exponential backtracking (ReDoS) when parsing maliciously crafted HTTP or multipart segment headers. This can be abused for denial of service (DoS) attacks against web applications using this library to parse request headers or multipart/form-data streams. Impact Any WSGI or ASGI application using multipart.parseformdata() directly or indirectly (e.g. while parsing multipart/form-data streams) is vulnerable. The slow-down is significant enough to block request handling threads for multiple seconds per request. Affected versions All versions up to and including 1.3.0 are affected. The issue is fixed in 1.2.2, 1.3.1 and 1.4.0-dev.
Recommended action: Upgrade to 1.3.1 or 1.2.2 by release line, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.