Review reviewHigh

CVE-2026-28356

defnull multipart, Red Hat AI Inference Server 3.2, Red Hat OpenShift AI 2.25

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.

CVSS: 7.5
EPSS: 0.72%
CISA KEV: Not listed
Published: 2026.03.13

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.72%

Technical severityCVSS 7.5

Vulnerability overview

Affected product and versions

Product: defnull multipart, Red Hat AI Inference Server 3.2, Red Hat OpenShift AI 2.25
Affected versions: >= >= 1.3.0, < 1.3.1, >= < 1.2.2
Fixed versions: No verified fixed-version field is available yet

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that defnull multipart, Red Hat AI Inference Server 3.2, Red Hat OpenShift AI 2.25 and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
CWE: CWE-1333