CVE-2026-74270: handshake: 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 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.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Modify the netlink handshake to require GENL_ADMIN_PERM (admin permission) when processing the DONE command (handshake_nl_done_doit), so unprivileged processes cannot forge DONE to prematurely tear down legitimate in-flight handshake requests.
Linux kernel netlink handshake (handshake_nl_done_doit) Require GENL_ADMIN_PERM for DONE command = enforce