CVE-2021-20718

mod_auth_openidc 2.4.0 to 2.4.7 allows a remote attacker to cause a denial-of-service (DoS) condition via unspecified vectors.

The product does not properly control the allocation and maintenance of a limited resource.

Name	Vendor	Start Version	End Version
Mod_auth_openidc	Openidc	2.4.0 (including)	2.4.7 (including)
Libapache2-mod-auth-openidc	Ubuntu	bionic	*
Libapache2-mod-auth-openidc	Ubuntu	esm-apps/focal	*
Libapache2-mod-auth-openidc	Ubuntu	focal	*
Libapache2-mod-auth-openidc	Ubuntu	groovy	*
Libapache2-mod-auth-openidc	Ubuntu	hirsute	*
Libapache2-mod-auth-openidc	Ubuntu	trusty	*
Libapache2-mod-auth-openidc	Ubuntu	upstream	*
Libapache2-mod-auth-openidc	Ubuntu	xenial	*

Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.

NVD	https://nvd.nist.gov/vuln/detail/CVE-2021-20718
CWE	https://cwe.mitre.org/data/definitions/400.html

Uncontrolled Resource Consumption