TL;DR is at the bottom (;
5 days ago this exploit development got published: [Wayback/Archive] snowcra5h/CVE-2023-38408: CVE-2023-38408 Remote Code Execution in OpenSSH’s forwarded ssh-agent.
It is about [Wayback/Archive] NVD – CVE-2023-38408 which there at NIST isn’t rated (yet?), neither at [Wayback/Archive] CVE-2023-38408 : The PKCS#11 feature in ssh-agent in OpenSSH before 9.3p2 has an insufficiently trustworthy search path, leading to remot.
However at [Wayback/Archive] CVE-2023-38408- Red Hat Customer Portal it scores 7.3 and [Wayback/Archive] CVE-2023-38408 | SUSE it did get a rating of 7.5, so since I mainly use OpenSuSE I wondered what to do as the CVE is formulated densely at [Wayback/Archive] www.qualys.com/2023/07/19/cve-2023-38408/rce-openssh-forwarded-ssh-agent.txt: it mentions Alice, but no Bob or Mallory (see Alice and Bob – Wikipedia).
Luckily, others readly already did the fine reading and emphasised the important bits, especially at [Wayback/Archive] RCE Vulnerability in OpenSSH’s SSH-Agent Forwarding: CVE-2023-38408 (note that instead of Alex, they actually mean Alice)
“A system administrator (Alice) runs SSH-agent on her local workstation, connects to a remote server with ssh, and enables SSH-agent forwarding with the -A or ForwardAgent option, thus making her SSH-agent (which is running on her local workstation) reachable from the remote server.”
According to researchers from Qualys, a remote attacker who has control of the host, which Alex has connected to, can load (dlopen()) and immediately unload (dlclose()) any shared library in /usr/lib* on Alice’s workstation (via her forwarded SSH-agent if it is compiled with ENABLE_PKCS11, which is the default).
The vulnerability lies in how SSH-agent handles forwarded shared libraries. When SSH-agent is compiled with ENABLE_PKCS11 (the default configuration), it forwards shared libraries from the user’s local workstation to the remote server. These libraries are loaded (dlopen()) and immediately unloaded (dlclose()) on the user’s workstation. The problem arises because certain shared libraries have side effects when loaded and unloaded, which can be exploited by an attacker who gains access to the remote server where SSH-agent is forwarded to.
Mitigations for the SSH-Agent Forwarding RCE Vulnerability
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