#VU51444 Double Free in OpenSSH - CVE-2021-28041

Vulnerability identifier: #VU51444

Vulnerability risk: Medium

CVSSv4.0: 4.4 [CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/U:Green]

CVE-ID: CVE-2021-28041

CWE-ID: CWE-415

Exploitation vector: Network

Exploit availability: No

Vulnerable software:
OpenSSH
Server applications / Remote management servers, RDP, SSH

Vendor: OpenSSH

Description

The vulnerability allows a remote attacker to execute arbitrary code on the target system.

The vulnerability exists due to a boundary error in ssh-agent. A remote attacker can trick the victim to connect to a server, where the attacker has root privileges, pass specially crafted data to the ssh client, trigger a double free error and execute arbitrary code on the target system.

Successful exploitation of this vulnerability may result in complete compromise of vulnerable system.

Mitigation
Install updates from vendor's website.

Vulnerable software versions

OpenSSH: 8.2p1 - 8.4p1

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External links
https://github.com/openssh/openssh-portable/commit/e04fd6dde16de1cdc5a4d9946397ff60d96568db
https://www.openssh.com/security.html
https://www.openssh.com/txt/release-8.5
https://www.openwall.com/lists/oss-security/2021/03/03/1

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote authenticated user via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.