ssh-agent in OpenSSH before 8.5 has a double free that may be relevant in a few less-common scenarios, such as unconstrained agent-socket access on a legacy operating system, or the forwarding of an agent to an attacker-controlled host.
https://www.oracle.com//security-alerts/cpujul2021.html
https://www.openwall.com/lists/oss-security/2021/03/03/1
https://www.openssh.com/txt/release-8.5
https://www.openssh.com/security.html
https://security.netapp.com/advisory/ntap-20210416-0002/
https://security.gentoo.org/glsa/202105-35
https://github.com/openssh/openssh-portable/commit/e04fd6dde16de1cdc5a4d9946397ff60d96568db