Vulnerability · Published Sep 20, 2022 · Assigned by NCSC.ch
CVE-2022-39956Partial 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
High 7.3
In plain English
A high-severity incorrect authorization in ModSecurity Core Rule Set from OWASP. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 1.2% (higher than 69% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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).
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | modsecurity-crs | 3.3.4-1 | DEBIAN-CVE-2022-39956 |
| Debian:13 | modsecurity-crs | 3.3.4-1 | DEBIAN-CVE-2022-39956 |
| Debian:14 | modsecurity-crs | 3.3.4-1 | DEBIAN-CVE-2022-39956 |
| Ubuntu:22.04:LTS | modsecurity-crs | no fix listed | UBUNTU-CVE-2022-39956 |
| Ubuntu:24.04:LTS | modsecurity-crs | no fix listed | UBUNTU-CVE-2022-39956 |
| Ubuntu:25.10 | modsecurity-crs | no fix listed | UBUNTU-CVE-2022-39956 |
| Ubuntu:26.04:LTS | modsecurity-crs | no fix listed | UBUNTU-CVE-2022-39956 |
| Ubuntu:26.10 | modsecurity-crs | no fix listed | UBUNTU-CVE-2022-39956 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| OWASP | ModSecurity Core Rule Set | 3.0.x3.1.xunspecified – through 3.2.1unspecified – through 3.3.2 |
Weakness: CWE-863 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
References
- https://coreruleset.org/20220919/crs-version-3-3-3-and-3-2-2-covering-several-cves/
- FEDORA-2022-90708b46e3 vendor-advisory
- FEDORA-2022-85a85c84b3 vendor-advisory
- FEDORA-2022-1fd73a5285 vendor-advisory
- [debian-lts-announce] 20230130 [SECURITY] [DLA 3293-1] modsecurity-crs security update mailing-list
- GLSA-202305-25 vendor-advisory
- https://lists.debian.org/debian-lts-announce/2025/08/msg00004.html