REDHAT-BUG-2344780: Medium severity OpenSSH OpenSSH client vulnerability
The OpenSSH client is vulnerable to an active machine-in-the-middle attack if the VerifyHostKeyDNS option is enabled (it is disabled by default): when a vulnerable client connects to a server, an active machine-in-the-middle can impersonate the server by completely bypassing the client's checks of the server's identity.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Disable the OpenSSH client option VerifyHostKeyDNS (it is disabled by default) to prevent active machine-in-the-middle impersonation that bypasses server identity checks.
OpenSSH client VerifyHostKeyDNS = disabled
Event History
Frequently Asked Questions
What is the severity of REDHAT-BUG-2344780?
The severity of REDHAT-BUG-2344780 is classified as high due to its potential for an active machine-in-the-middle attack.
How does REDHAT-BUG-2344780 affect OpenSSH clients?
REDHAT-BUG-2344780 affects OpenSSH clients by allowing an active machine-in-the-middle to impersonate the server when the VerifyHostKeyDNS option is enabled.
How do I fix REDHAT-BUG-2344780?
To fix REDHAT-BUG-2344780, disable the VerifyHostKeyDNS option in the OpenSSH client configuration if it is enabled.
Which versions of OpenSSH are affected by REDHAT-BUG-2344780?
All versions of the OpenSSH client that have the VerifyHostKeyDNS option enabled are vulnerable to REDHAT-BUG-2344780.
Is the VerifyHostKeyDNS option enabled by default in OpenSSH clients?
No, the VerifyHostKeyDNS option is disabled by default in OpenSSH clients.