CVE-2021-28041: 
NixOS vulnerability analysis and mitigation

CVE-2021-28041 is a double-free memory corruption vulnerability discovered in ssh-agent in OpenSSH versions between 8.2 and 8.4 (inclusive). The vulnerability was disclosed on March 3, 2021, and was fixed in OpenSSH 8.5 (OpenSSH Release, OpenSSH Security).

The vulnerability is a double-free memory corruption issue in the ssh-agent component. This flaw could be exploited in specific scenarios where an attacker has access to the agent socket. The vulnerability has been assigned a CVSS v3.1 base score of 7.1 (HIGH) with the vector string CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:U/C:H/I:H/A:H (NVD).

A successful exploitation of this vulnerability could lead to disclosure of sensitive information, addition or modification of data, or Denial of Service (DoS). The most likely scenario for exploitation is when a user forwards an agent either to an account shared with a malicious user or to a host with an attacker holding root access (OpenSSH Release).

The vulnerability was fixed in OpenSSH 8.5. Users should upgrade to this version or later to address the issue. The vulnerability is mitigated by socket peer user identity checking and double-free protection in malloc(3) on systems that support these features (OpenSSH Security).