CVE-2026-80989 net: thunderbolt: Mark the connection down when bringing it up fails
A use-after-free in the Linux kernel Thunderbolt network driver allows attackers to cause a denial of service or potentially execute code via crafted connection failures.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-80989?
CVE-2026-80989 is a high-severity use after free vulnerability in Linux, published on 11 Sep 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:
net: thunderbolt: Mark the connection down when bringing it up fails
Every failure path in tbnet_connected_work() undoes its own work and returns without clearing login_sent, so the connection still looks established. The next tbnet_tear_down() therefore takes its main branch and repeats a teardown that already happened: it stops rings that are already stopped, which is a dev_WARN() and fatal under panic_on_warn, and it releases net->remote_transmit_path even on the HopID mismatch path, where this connection never owned that id, silently freeing one that someone else is still using.
Clear login_sent on those paths. That is enough for tbnet_tear_down() to leave the unwound state alone, and login_received has to stay set: it records that the peer has logged in and carries the transmit path it gave us, which nothing on this side can make the peer send again. Two things change beyond keeping the teardown out of the way: the logout request in that block is no longer sent, and the peer's next login request now re-queues our login work rather than connected_work, giving the connection a fresh login instead of a retry on stale state.
Which versions are affected by CVE-2026-80989?
How do I fix CVE-2026-80989?
Apply the vendor's patch.
Upgrade to the fixed version. These bugs are found with fuzzing and sanitisers and avoided by memory-safe languages. More about Use after free.
Is CVE-2026-80989 being exploited?
There is no known exploitation of CVE-2026-80989 in the wild and no public exploit code.
Sources
Also known as AZL-100764, BELL-CVE-2026-80989, DEBIAN-CVE-2026-80989, GHSA-fm3c-92pm-qq7p, UBUNTU-CVE-2026-80989.