CVE-2026-74270

In the Linux kernel, the following vulnerability has been resolved:

handshake: Require admin permission for DONE command

ACCEPT and DONE are the two downcalls of the handshake genl family, both intended for use by the trusted handshake agent (tlshd). ACCEPT already requires GENLADMINPERM; DONE has no privilege check at all.

The fd-lookup in handshakenldonedoit() only confirms that some pending handshake request exists for the supplied sockfd; it does not authenticate the sender. An unprivileged process that guesses or observes a valid sockfd can therefore submit a DONE with HANDSHAKEADONESTATUS == 0, leaving the kernel consumer to proceed as if the handshake succeeded. A non-zero status on a forged DONE tears down a legitimate in-flight handshake before tlshd can report its real result.