CVE-2026-80990 in Linux
Summary
by MITRE • 09/12/2026
In the Linux kernel, the following vulnerability has been resolved:
net: thunderbolt: Release the Rx HopID that was handed out on mismatch
tb_xdomain_alloc_in_hopid() passes the wanted HopID to ida_alloc_range() as the lower bound, so a taken id is not an error there: the allocator returns the next free one above it. tbnet_connected_work() asks for the peer's transmit path, treats any other id as a failure and returns without releasing what it got, so that allocation stays live for the rest of the XDomain connection with nothing left holding a reference to it.
Release the id when it is not the one we asked for, the same way the error unwind at the end of the function releases the expected one.
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Analysis
by VulDB Data Team • 09/12/2026
The vulnerability identified in the Linux kernel's Thunderbolt networking subsystem involves a resource leak within the XDomain connection management logic. Specifically, the issue resides in the tb_xdomain_alloc_in_hopid() function and its interaction with the ida_alloc_range allocator. When establishing an outbound communication path for an XDomain device, the system attempts to allocate a specific HopID, which serves as an identifier for network channels. The allocation routine is designed such that if the requested ID is already in use, it does not return an error but instead allocates the next available free ID above the requested value. This behavior is standard for range-based integer allocators like ida_alloc_range, where flexibility in assignment ensures efficient resource utilization without immediate failure on contention.
The critical flaw emerges in tbnet_connected_work(), which orchestrates the connection setup process. After requesting a HopID from the peer's transmit path allocation routine, this function checks if the returned ID matches the originally requested one. If there is any mismatch, indicating that a different ID was allocated due to prior usage of the preferred slot, the current implementation treats this discrepancy as a failure condition. Consequently, the code returns early without executing the necessary cleanup routines. This oversight means that while the operation fails logically from the perspective of the connection setup, the previously acquired HopID remains allocated in the system's internal data structures.
This leads to a persistent resource leak where an unused HopID stays reserved for the duration of the XDomain connection. Since no other component holds a reference to this misallocated ID and it is never released due to the early return path, it becomes orphaned memory within the kernel's allocation pool. Over time, particularly in environments with frequent Thunderbolt device connections or high churn rates, these leaked HopIDs can accumulate. This gradual depletion of available identifiers may eventually lead to resource exhaustion, preventing new XDomain connections from being established and potentially causing network connectivity issues for devices relying on Thunderbolt networking capabilities.
From a security and stability perspective, this vulnerability is classified under CWE-401, which describes the missing release of memory after successful allocation. In terms of attack vectors or operational impact, while primarily a denial-of-service risk through resource exhaustion rather than arbitrary code execution, it degrades system reliability. The ATT&CK framework does not have a direct mapping for this specific kernel-level leak in standard consumer scenarios, but it aligns with techniques involving resource consumption to disrupt service availability. Mitigation requires modifying the tbnet_connected_work() function to ensure that any HopID obtained from the allocation routine is released if it does not match the expected value or if subsequent steps fail. This ensures proper cleanup and maintains the integrity of the ID pool, preventing long-term degradation of Thunderbolt networking functionality in Linux-based systems.