CVE-2026-74270
HighCVSS 7.8Exploitation Probability (EPSS)
Low risk3th percentile - higher than 3% of all known CVEs
Summary
In the Linux kernel, the handshake subsystem now requires admin permission for the DONE command. Previously, DONE had no privilege check, allowing an unprivileged process to send a forged DONE with status 0, causing the kernel to treat the handshake as successful, or with a non-zero status, tearing down a legitimate in-flight handshake.
Risk Assessment
The risk includes impersonation of the trusted handshake agent by an unprivileged user, potentially leading to connection integrity compromise or service disruption.
Recommendation
Apply the kernel patch that requires admin permission for the DONE command to prevent unauthorized operations.
Original NVD description (English source)
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.