CVE-2026-80989
nicheIncorrect HopID free and panic_on_warn DoS in Linux kernel Thunderbolt networking
A bug in the Linux kernel's Thunderbolt networking driver (net/thunderbolt, tbnet) leaves login_sent set when connection bring-up fails, so the driver still considers a half-unwound connection established. A later teardown then re-stops DMA rings that are already stopped, which fires a dev_WARN() that is fatal on systems booted with panic_on_warn=1, and on the HopID-mismatch path it releases the remote transmit path (HopID) even though that connection never owned it — silently freeing a Thunderbolt HopID still in use by another connection, which can lead to memory-safety corruption of the shared path state. The flaw is triggered by a failed login/bring-up exchange with a peer on the other end of a Thunderbolt IP link (adjacent-network attack vector, no privileges or user interaction required), and is rated high severity (CVSS 3.1: 8.8) with high confidentiality, integrity, and availability impact. Only systems actually using Thunderbolt networking — host-to-host Thunderbolt IP links such as Apple Thunderbolt Bridge-style setups on Linux — are exposed. There is no public PoC and no known in-the-wild exploitation; the issue is not in CISA's KEV catalog.
What to do: Apply a kernel containing the upstream fix once it reaches your distribution's stable releases. Check whether the driver is actually in use (e.g., 'lsmod | grep thunderbolt_net' or the presence of Thunderbolt IP network interfaces) and disable Thunderbolt networking if you don't need host-to-host Thunderbolt links. As defense-in-depth, avoid booting production systems with panic_on_warn=1 and restrict physical access to Thunderbolt ports, since exploitation requires an adjacent peer on the Thunderbolt connection.
| Linux kernel (net: thunderbolt / thunderbolt-net driver) | — |
Order-of-magnitude estimate by the model from install counts, market share and public scan data it knows; verify before quoting.
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.
- Vector
- CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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