A vulnerability, which was classified as problematic, was found in OWASP ModSecurity Core Rule Set up to 3.1.0. Affected is an unknown functionality of the file /rules/REQUEST-933-APPLICATION-ATTACK-PHP.conf. The manipulation with an unknown input leads to a incorrect regex vulnerability. CWE is classifying the issue as CWE-185. The product specifies a regular expression in a way that causes data to be improperly matched or compared. This is going to have an impact on availability. CVE summarizes:

An issue was discovered in OWASP ModSecurity Core Rule Set (CRS) through 3.1.0. /rules/REQUEST-933-APPLICATION-ATTACK-PHP.conf allows remote attackers to cause a denial of service (ReDOS) by entering a specially crafted string with $a# at the beginning and nested repetition operators. NOTE: the software maintainer disputes that this is a vulnerability because the issue cannot be exploited via ModSecurity

The bug was discovered 04/15/2019. The weakness was disclosed 04/21/2019. This vulnerability is traded as CVE-2019-11391 since 04/20/2019. It is possible to launch the attack remotely. The exploitation doesn't require any form of authentication. There are known technical details, but no exploit is available.

The vulnerability was handled as a non-public zero-day exploit for at least 6 days. During that time the estimated underground price was around $0-$5k. The real existence of this vulnerability is still doubted at the moment.

There is no information about possible countermeasures known. It may be suggested to replace the affected object with an alternative product.

The entries VDB-133931, VDB-133930, VDB-133929 and VDB-133928 are pretty similar.

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• OWASP

Name

• ModSecurity Core Rule Set

Version

• 3.0
• 3.1

License

• open-source

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