The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6 and other products, allows remote attackers to bypass integrity checks such that some packets are omitted (from the extension negotiation message), and a client and server may consequently end up with a connection for which some security features have been downgraded or disabled, aka a Terrapin attack. This occurs because the SSH Binary Packet Protocol (BPP), implemented by these extensions, mishandles the handshake phase and mishandles use of sequence numbers. For example, there is an effective attack against SSH's use of ChaCha20-Poly1305 (and CBC with Encrypt-then-MAC). The bypass occurs in chacha20-poly1305@openssh.com and (if CBC is used) the -etm@openssh.com MAC algorithms. This also affects Maverick Synergy Java SSH API before 3.1.0-SNAPSHOT, Dropbear through 2022.83, Ssh before 5.1.1 in Erlang/OTP, PuTTY before 0.80, AsyncSSH before 2.14.2, golang.org/x/crypto before 0.17.0, libssh before 0…

Like many other SSH implementations, Apache MINA SSHD suffered from the issue that is more widely known as CVE-2023-48795. An attacker that can intercept traffic between client and server could drop certain packets from the stream, potentially causing client and server to consequently end up with a connection for which some security features have been downgraded or disabled, aka a Terrapin attack The mitigations to prevent this type of attack were implemented in Apache MINA SSHD 2.12.0, both client and server side. Users are recommended to upgrade to at least this version. Note that both the client and the server implementation must have mitigations applied against this issue, otherwise the connection may still be affected.