CVE-2021-3601

A flaw was found in the way OpenSSL will accept a certificate with explicitly set Basic Constraints to CA:FALSE as a valid CA if it is present in the trusted bundle. This flaw allows an attacker with access to a private key, of which the corresponding certificate is in the trust bundle, to use this flaw for MITM to any connection from the victim machine.

It was found that OpenSSL will accept a certificate with explicitly set Basic Constraints to CA:FALSE as a valid CA if it is present in the trusted bundle. The exploitability of this bug is limited; the attacker needs to get access to a private key of which the corresponding certificate is in the trust bundle. The attacker is able to leverage this certificate to MITM any connection from the victim machine, not just ones to the specific server that uses the self-signed certificate.

The CVSS score(s) listed for this vulnerability do not reflect the associated product's status, and are included for informational purposes to better understand the severity of this vulnerability.

Red Hat recommends not to include self-signed server certificates in system trust bundle, even with CA:FALSE, as they are considered full-fledged Certificate Authorities.