CVE-2026-28356
HIGH
GHSA-p2m9-wcp5-6qw3
CVSS Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Lifecycle Timeline
4Description
multipart is a fast multipart/form-data parser for python. Prior to 1.2.2, 1.3.1 and 1.4.0-dev, the parse_options_header() 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. The issue is fixed in 1.2.2, 1.3.1 and 1.4.0-dev.
Analysis
High severity vulnerability in Python multipart. The `parse_options_header()` 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. …
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Remediation
Within 24 hours: Inventory all applications and services using the Python multipart library and assess exposure to untrusted HTTP multipart requests. Within 7 days: Implement WAF rules to filter malicious multipart headers and restrict multipart upload sizes; consider temporarily disabling file upload features if business-critical. …
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