In early 2026, Teleport engaged NCC Group's Cryptography Services practice to perform a review of the Go SSH package, x/crypto/ssh, which implements both the client and server-side portions of the SSH protocol. A total of 15 findings were documented, along with a small number of non-security engagement notes.
The review found that the code was generally well-structured and documented and recommends ensuring that these high standards are maintained going forward. Predictable modifications to the protocol to include more upcoming post-quantum cryptographic algorithms will require some corresponding support code, which should carefully follow the existing code framework.
NCC Group would also like to thank Geomys, who provided technical support and coordinated remediation for all findings identified during the review, including coordinating disclosure. As a result of this collaboration, a total of 9 CVEs were filed based on findings in the report:
- CVE-2026-39828 - ssh: bypass of certificate restrictions
- CVE-2026-39829 - ssh: pathological RSA/DSA parameters may cause DoS
- CVE-2026-39830 - ssh: client can cause server deadlock on unexpected responses
- CVE-2026-39831 - ssh: bypass of FIDO/U2F security keys physical interaction
- CVE-2026-39832 - ssh/agent: agent constraints dropped when forwarding keys
- CVE-2026-39833 - ssh/agent: key constraints not enforced
- CVE-2026-39834 - ssh: infinite loop on large channel writes
- CVE-2026-39835 - ssh: server panic during CheckHostKey/Authenticate
- CVE-2026-46598 - ssh/agent: pathological inputs can lead to client panic
These issues have been addressed as of May 22, 2026 in the v0.52.0 release of x/crypto, as announced on the Golang Announce group.