High [CVE-2026-74270] Require admin permission for DONE command

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 GENL_ADMIN_PERM; DONE has no privilege check at all.

The fd-lookup in handshake_nl_done_doit() 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 HANDSHAKE_A_DONE_STATUS == 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. An unprivileged local attacker can exploit a missing permission check in the 'DONE' command of the handshake general Netlink (genl) family.

By guessing or observing a valid socket identifier, the attacker can either force the kernel to believe a handshake succeeded, potentially leading to unauthorized operations, or disrupt an ongoing legitimate handshake, causing a Denial of Service (DoS). Red Hat severity: Important — CVSS 7 (CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H).

Weakness: CWE-290. Affected Red Hat products: Red Hat Enterprise Linux 10; Red Hat Enterprise Linux 9.