CVE Catalog

CVE-2026-28356

HighCVSS 7.5
Published: Updated: Translated: NVD NIST

Exploitation Probability (EPSS)

Elevated risk
0.72%

51th percentile - higher than 51% of all known CVEs

Summary

The multipart library for Python contains a ReDoS vulnerability in the parse_options_header() function due to an ambiguous alternation in the regular expression. This can cause exponential backtracking when processing maliciously crafted HTTP or multipart/form-data headers.

Risk Assessment

An attacker can exploit this vulnerability to perform a Denial of Service (DoS) attack on web applications using the multipart library to parse request headers or multipart/form-data streams, potentially leading to service unavailability.

Recommendation

Immediately update the multipart library to version 1.2.2, 1.3.1, or 1.4.0-dev, depending on the branch used, to eliminate the ReDoS vulnerability.

Related vulnerabilities

Original NVD description (English source)

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.

Vulnerability data from NVD (NIST) · CISA KEV · EPSS