OpenSSH: The Tale of the Disappearing Host Key and the Memory Munching MitM!
OpenSSH’s VerifyHostKeyDNS-enabled client has vulnerabilities that make it prone to a MitM attack and a DoS attack. The client can fall for an imposter server, while both client and server can be hit by overused memory during a key exchange. Remember, even in the world of tech, appearances can be deceiving!
Hot Take:
Remember the good old days when the biggest threat to your SSH connection was a forgotten password? Well, buckle up, because now it’s a man-in-the-middle attack with a side of denial-of-service, courtesy of OpenSSH’s latest vulnerabilities. It’s like a cybersecurity soap opera where your server gets identity crises and memory blackouts!
Key Points:
- Two vulnerabilities in OpenSSH: MitM attack (CVE-2025-26465) and DoS attack (CVE-2025-26466).
- MitM attack exploits VerifyHostKeyDNS feature, bypassing server identity checks.
- DoS attack causes asymmetric resource consumption, affecting memory and CPU.
- MitM attack requires client to run out of memory using crafted server responses.
- Default settings on FreeBSD made it vulnerable for a decade, but fixes are now available.
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