CVE-2026-74270 handshake: Require admin permission for DONE command
An unprivileged local attacker can forge handshake completion messages to bypass security checks or disrupt legitimate TLS handshakes.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-74270?
CVE-2026-74270 is a high-severity missing authorization vulnerability in Linux, published on 15 Aug 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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.
Which versions are affected by CVE-2026-74270?
How do I fix CVE-2026-74270?
Apply the vendor's patch.
Upgrade, and check permissions on every request on the server, not only in the interface. More about Missing authorization.
Is CVE-2026-74270 being exploited?
There is no known exploitation of CVE-2026-74270 in the wild and no public exploit code.
Sources
Also known as BELL-CVE-2026-74270, DEBIAN-CVE-2026-74270, GHSA-fc6x-h5h8-wjr3, UBUNTU-CVE-2026-74270.