Denial of service in OWASP ModSecurity Core Rule Set (CRS)

1) Incorrect Regular Expression

EUVDB-ID: #VU72100

Risk: Medium

CVSSv3.1: 6.5 [CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H/E:U/RL:O/RC:C]

CVE-ID: CVE-2019-11387

CWE-ID: CWE-185 - Incorrect Regular Expression

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to incorrect ruleset in /rules/REQUEST-942-APPLICATION-ATTACK-SQLI.conf. A remote attacker can pass a specially crafted string with nested repetition operators and perform regular expression denial of service (ReDos) attack.

Mitigation

Install update from vendor's website.

Vulnerable software versions

OWASP ModSecurity Core Rule Set (CRS): 3.0.0 - 3.1.0

External links

http://github.com/SpiderLabs/owasp-modsecurity-crs/issues/1359
http://github.com/SpiderLabs/owasp-modsecurity-crs/blob/v3.1/dev/CHANGES
http://coreruleset.org/20190627/announcement-owasp-modsecurity-core-rule-set-version-3-1-1/

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

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