CVE-2026-97629: How a Third Ticket-Key Slot Allowed a Forged TLS Session

Of the five flaws fixed in NGINX 1.30.6 and 1.31.7, CVE-2026-97629 is the one that breaks an authentication assumption rather than a memory boundary. Under specific conditions an attacker can present a TLS session ticket that NGINX will accept and decrypt using key material it never initialized, producing what F5 calls a forged session. The practical consequence is that certificate-based client authentication can be bypassed without any private key.

Background: how ticket keys are supposed to work

Session tickets let a client resume a TLS session without a full handshake. The server encrypts the session state with a ticket key and hands the result to the client; on resumption the client returns the ticket and the server decrypts it with the same key.

Historically operators managed those keys themselves.…