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Terrapin
Terrapin is an SSH Binary Packet Protocol prefix-truncation vulnerability affecting OpenSSH before 9.6 and numerous other SSH implementations. Incorrect handshake and packet sequence-number handling allows an active machine-in-the-middle attacker to manipulate sequence numbers before encryption begins and subsequently remove initial encrypted packets without triggering integrity-check failures. Practical attacks affect connections using ChaCha20-Poly1305 or CBC encryption combined with Encrypt-then-MAC. Removing the SSH extension-negotiation message can cause clients and servers to establish connections with security features downgraded or disabled.
What it means and what to do now: patch path, interim mitigations, and the assume-compromise checklist.
What an attacker gets, and what they’ve been doing with it.
Successful exploitation compromises SSH handshake integrity and can silently suppress negotiated security extensions. Depending on the implementation and version, this can weaken client authentication algorithm selection or disable keystroke-timing countermeasures. It can also enable exploitation of separate implementation flaws that would otherwise be unreachable. Terrapin alone does not establish arbitrary code execution, general session decryption, or complete system compromise.
If you can’t patch tonight, do this now.
Until updates are deployed, prevent negotiation of ChaCha20-Poly1305 and CBC with Encrypt-then-MAC; prefer unaffected alternatives such as AES-GCM. Apply algorithm restrictions to relevant client and server configurations. Where supported, disable SSH management temporarily and use a trusted alternative management interface. Restrict management access to trusted networks. For affected Jenkins CLI clients, avoid the non-default SSH connection mode until patched.
Patch, then assume compromise.
Update affected SSH clients and servers to vendor-fixed releases and ensure both endpoints support and negotiate the strict key-exchange countermeasure. Fixed releases include OpenSSH 9.6, PuTTY 0.80, AsyncSSH 2.14.2, golang.org/x/crypto 0.17.0, libssh 0.10.6, Paramiko 3.4.0, and Russh 0.40.2. Vendor-supported backported fixes are also applicable; for example, Red Hat provides libssh 0.9.6-4.el8_6 through RHSA-2024:0538. Restart applications using updated SSH libraries. Update embedded SSH components through the applicable product security release.
No validated public exploits yet. Hidden: 5 rejected by Mallory's analysis as not a working exploit; 2 not yet analyzed, such as Exploit-DB entries.
Products and vendors Mallory has correlated with this vulnerability. Open in Mallory to drill down to specific CPE configurations and version ranges.
106 sources tracked across advisories, community write-ups, and news. New activity surfaces here as Mallory finds it.