CVE-2026-55200

This flaw is in libssh2, a library commonly used by programs to handle SSH connections. An attacker can send a specially malformed SSH message with an invalid “packet length,” which can trick the software into writing beyond where it should in memory—leading to crashes or, in the worst case, letting the attacker run code. Think of it like a network message that lies about how big the payload is, causing the receiver to write into the wrong memory space.

This matters if you run software that uses libssh2 to make SSH connections (for example, tools that pull files over SSH or remote management components built on libssh2). Because the vulnerability can be triggered remotely and does not require authentication, it’s most relevant when your client connects to SSH servers you don’t fully control.
Reachability gate: only a risk if the vulnerable libssh2 SSH client read path is reachable from the network you allow (in practice, if your software connects to attacker-controlled or untrusted SSH endpoints).

This is AMBER because it is a high-impact memory corruption flaw in a widely used SSH library, meaning a network attacker could potentially achieve code execution. Even though there’s no confirmed in-the-wild exploitation report, a public proof-of-concept exists, and the vendor has provided a fix—so you should prioritize upgrading.