CVE-2022-39956

Partial rule set bypass in OWASP ModSecurity Core Rule Set for HTTP multipart requests using character encoding in the Content-Type or Content-Transfer-Encoding header

Published Sep 20, 2022 CVSS 3.1 · 7.3 High EPSS 1.2% KEV · Not listed
Description
The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).

Remediation

Vendor Solution

upgrade to 3.2.2 or 3.3.3

Tracking

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Advisories

Source ID Title
Debian DLA Debian DLA DLA-3283-1 modsecurity-apache security update
Debian DLA Debian DLA DLA-3293-1 modsecurity-crs security update
Debian DLA Debian DLA DLA-4265-1 modsecurity-crs security update
EUVD EUVD EUVD-2022-42400 The OWASP ModSecurity Core Rule Set (CRS) is affected by a partial rule set bypass for HTTP multipart requests by submitting a payload that uses a character encoding scheme via the Content-Type or the deprecated Content-Transfer-Encoding multipart MIME header fields that will not be decoded and inspected by the web application firewall engine and the rule set. The multipart payload will therefore bypass detection. A vulnerable backend that supports these encoding schemes can potentially be exploited. The legacy CRS versions 3.0.x and 3.1.x are affected, as well as the currently supported versions 3.2.1 and 3.3.2. Integrators and users are advised upgrade to 3.2.2 and 3.3.3 respectively. The mitigation against these vulnerabilities depends on the installation of the latest ModSecurity version (v2.9.6 / v3.0.8).
History
Type Values Removed Values Added
Metrics ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'none', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
NCSC.ch
Published
Updated
Nov 3, 2025, 7:27 PM
Reserved
Sep 5, 2022, 12:00 AM
Status
Modified
Published
Sep 20, 2022, 7:15 AM
Modified
Jun 17, 2026, 4:58 AM
Severity
Moderate
Public date
Sep 19, 2022, 12:00 AM