Bug 2555174 (CVE-2026-98693)

Summary: CVE-2026-98693 kernel: thunderbolt: Hold a router reference for each allocated HopID
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, watson-tool-maintainers
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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A flaw was found in the Linux kernel's Thunderbolt driver. A physically proximate user or local attacker could trigger a Denial of Service (DoS) and crash the system by disconnecting a device or unbinding the driver while DisplayPort tunnel operations are still active. This issue occurs because the driver fails to maintain proper router reference counts during connection routing, allowing device structures to be freed prematurely while background tasks are still running. When the remaining tasks complete, cleanup operations attempt to access already freed memory, leading to memory corruption and kernel instability.
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Description OSIDB Bzimport 2026-10-18 15:58:36 UTC 
In the Linux kernel, the following vulnerability has been resolved:

thunderbolt: Hold a router reference for each allocated HopID

tb_stop() drops the reference to all DP tunnels but does not deactivate
them, thus nothing cancels a dprx_work still in flight (which holds its
own tunnel reference) and the tunnel can outlive tb_switch_remove(). The
HopID releases in tb_path_free() then operate on freed IDAs and trigger
warnings like

  ida_free called for id=8 which is not allocated.

This can be triggered by unbinding the driver while a DP tunnel is still
waiting for the DPRX capabilities read to finish. On the Apple NHI
unplugging the cable runs into just that reliably because the read can
never finish right now and because the unplug powers down the entire
USB4 complex and removes the NHI device.

Take a router reference whenever an input or output HopID is allocated
and drop it again after the HopID is released. This keeps the ports and
their HopID IDAs alive for as long as they are used.

The KUnit tests allocate routers without ever registering their devices
so initialize the embedded struct device there as well and drop its
initial reference when the test is finished.
Comment 1 Mauro Matteo Cascella 2026-10-22 04:02:18 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-98693.mbox