#VU78454 Untrusted search path in OpenSSH - CVE-2023-38408

Vulnerability identifier: #VU78454

Vulnerability risk: Medium

CVSSv4.0: 6.6 [CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:P/U:Green]

CVE-ID: CVE-2023-38408

CWE-ID: CWE-426

Exploitation vector: Network

Exploit availability: Yes

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

Vendor: OpenSSH

Description

The vulnerability allows a remote attacker to compromise the affected system.

The vulnerability exists due to usage of an insecure search path within the PKCS#11 feature in ssh-agent. A remote attacker can trick the victim into connecting to a malicious SSH server and execute arbitrary code on the system, if an agent is forwarded to an attacker-controlled system.

Note, this vulnerability exists due to incomplete fix for #VU2015 (CVE-2016-10009).

Mitigation
Install updates from vendor's website.

Vulnerable software versions

OpenSSH: 7.0 - 9.3p1

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External links
https://github.com/openbsd/src/commit/7bc29a9d5cd697290aa056e94ecee6253d3425f8
https://www.openssh.com/txt/release-9.3p2
https://www.qualys.com/2023/07/19/cve-2023-38408/rce-openssh-forwarded-ssh-agent.txt
https://blog.qualys.com/vulnerabilities-threat-research/2023/07/19/cve-2023-38408-remote-code-execution-in-opensshs-forwarded-ssh-agent
https://news.ycombinator.com/item?id=36790196
https://github.com/openbsd/src/commit/f8f5a6b003981bb824329dc987d101977beda7ca
https://github.com/openbsd/src/commit/f03a4faa55c4ce0818324701dadbf91988d7351d
https://www.openssh.com/security.html
https://security.gentoo.org/glsa/202307-01

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Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability. However, proof of concept for this vulnerability is available.