WAF ruleset bypass in OWASP ModSecurity Core Rule Set (CRS)

1) Protection mechanism failure

EUVDB-ID: #VU54495

Risk: Medium

CVSSv3.1: 5.5 [CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-35368

CWE-ID: CWE-693 - Protection Mechanism Failure

Exploit availability: No

Description

The vulnerability allows a remote attacker to bypass implemented security restrictions.

The vulnerability exists due to insufficient implementation of security measures within the default CRS ruleset. An attacker can bypass implemented security restrictions and exploit vulnerabilities in the CMS that is protected with ModSecurity with the OWASP ModSecurity Core Rule Set (CRS).

Mitigation

Install updates from vendor's website.

Vulnerable software versions

OWASP ModSecurity Core Rule Set (CRS): 3.0.0 - 3.3.0

External links

http://coreruleset.org/20210630/cve-2021-35368-crs-request-body-bypass/

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.