CVE-2023-48795
MediumCVSS 5.9Exploitation Probability (EPSS)
Very high risk100th percentile - higher than 100% of all known CVEs
Summary
The Terrapin vulnerability in the SSH transport protocol affects OpenSSH before 9.6 and many other SSH implementations. A remote attacker can bypass integrity checks by omitting some packets during extension negotiation, causing security features to be downgraded or disabled. This impacts algorithms such as ChaCha20-Poly1305 and CBC with Encrypt-then-MAC.
Risk Assessment
An attacker can weaken or disable SSH session security, potentially enabling further attacks on data confidentiality and integrity. Organizations using vulnerable SSH implementations are at risk of traffic interception or modification.
Recommendation
Update all used SSH implementations to patched versions (e.g., OpenSSH 9.6 or later) and disable vulnerable algorithms such as [email protected] and CBC with [email protected] where possible.
Other vulnerabilities in SSH
See all- CVE-2026-56854High
The source-address critical option in the Permissions returned by an authentication callback was only enforced for the PublicKeyCallback and VerifiedPublicKeyCallback paths, extending the fix for CVE-2026-46595. Permissions returned by the PasswordCallback, KeyboardInteractiveCallback, NoClientAuthCallback, and GSSAPIWithMICConfig.AllowLogin callbacks were not validated against the client's remote address, so a source-address restriction set by those callbacks was silently ignored. The check is now applied to the Permissions returned by any authentication callback.
- CVE-2026-39828Medium
In SSH, when an authentication callback returned PartialSuccessError with non-nil Permissions, those permissions were silently discarded. This could drop certificate restrictions like force-command after a second factor. Returning non-nil Permissions with PartialSuccessError now results in a connection error.
- CVE-2000-0217Medium
The default configuration of SSH allows X forwarding, which could allow a remote attacker to control a client's X sessions via a malicious xauth program.
- CVE-1999-1231Medium
ssh version 2.0.12, and possibly other versions, allows valid usernames to attempt to enter the correct password multiple times, but only prompts for a password once for an invalid username. This allows remote attackers to determine user account names on the server.
- CVE-1999-1159Medium
SSH version 2.0.11 and earlier allows local users to request remote forwarding from privileged ports without being root.
Original NVD description (English source)
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 [email protected] and (if CBC is used) the [email protected] 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 0.10.6, libssh2 through 1.11.0, Thorn Tech SFTP Gateway before 3.4.6, Tera Term before 5.1, Paramiko before 3.4.0, jsch before 0.2.15, SFTPGo before 2.5.6, Netgate pfSense Plus through 23.09.1, Netgate pfSense CE through 2.7.2, HPN-SSH through 18.2.0, ProFTPD before 1.3.8b (and before 1.3.9rc2), ORYX CycloneSSH before 2.3.4, NetSarang XShell 7 before Build 0144, CrushFTP before 10.6.0, ConnectBot SSH library before 2.2.22, Apache MINA sshd through 2.11.0, sshj through 0.37.0, TinySSH through 20230101, trilead-ssh2 6401, LANCOM LCOS and LANconfig, FileZilla before 3.66.4, Nova before 11.8, PKIX-SSH before 14.4, SecureCRT before 9.4.3, Transmit5 before 5.10.4, Win32-OpenSSH before 9.5.0.0p1-Beta, WinSCP before 6.2.2, Bitvise SSH Server before 9.32, Bitvise SSH Client before 9.33, KiTTY through 0.76.1.13, the net-ssh gem 7.2.0 for Ruby, the mscdex ssh2 module before 1.15.0 for Node.js, the thrussh library before 0.35.1 for Rust, and the Russh crate before 0.40.2 for Rust.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS