CVE-2026-98392 in Linux
Summary
by MITRE • 10/14/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: btintel_pcie: fix tx_handle bounds off-by-one
Valid indices into txq->urbd0s/tfds/bufs are 0..txq->count-1, so tfd_index == txq->count is already out of range. Change the guard in btintel_pcie_msix_tx_handle() from '> txq->count' to '>= txq->count'.
This issue was reported by Claude Mythos.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 10/14/2026
The Linux kernel Bluetooth subsystem, specifically within the Intel PCIe driver module known as btintel_pcie, contained a critical off-by-one error in its transmit buffer handling logic. This vulnerability arises from an incorrect boundary check when processing interrupt service routines for transmission completion events. The core issue lies in how the driver validates indices before accessing internal data structures such as urbd0s, tfds, and bufs within the txq structure. These arrays are allocated with a size defined by txq->count, meaning that valid memory access is restricted to indices ranging from zero up to count minus one. Any index equal to or greater than count falls outside the bounds of the allocated memory region, leading to potential out-of-bounds read operations if not properly guarded against.
The specific flaw resides in the btintel_pcie_msix_tx_handle function, which processes transmission completions via Message Signaled Interrupts (MSI-X). The original code utilized a greater-than comparison operator when checking whether tfd_index exceeded txq->count. This logic incorrectly allowed an index exactly equal to txq->count to pass through the validation check and proceed into memory access routines. Since array indexing in C is zero-based, an index value matching the total count represents the first invalid position immediately following the last valid element. By failing to reject this specific boundary condition, the driver permitted access to memory locations that were not allocated for use by this queue structure, creating a pathway for unauthorized data retrieval or corruption depending on what resides in adjacent kernel memory space.
From a technical perspective, this vulnerability is classified under CWE-193 Off-by-One Error and potentially CWE-787 Out-of-bounds Read if the subsequent operations involve reading from these invalid indices. The operational impact of such an error can vary significantly based on system state and memory layout at the time of exploitation. In benign scenarios, accessing uninitialized or unmapped kernel memory may result in a null pointer dereference or general protection fault, causing a local denial of service through a kernel panic or crash. However, if adjacent memory contains sensitive information or control structures, an attacker with physical access to the device or who can trigger specific Bluetooth transmission patterns might leverage this out-of-bounds read to leak kernel memory contents. This could facilitate further privilege escalation attacks by revealing cryptographic keys, process identifiers, or other security-critical data residing in the kernel address space.
The vulnerability highlights the importance of strict boundary validation in low-level driver development where manual memory management is prevalent. The fix implemented involves changing the conditional guard from a greater-than comparison to a greater-than-or-equal-to comparison for txq->count. This simple arithmetic adjustment ensures that any index equaling or exceeding the allocated count is immediately rejected, thereby preventing access to invalid memory regions. Such corrections are essential for maintaining the integrity of kernel subsystems and ensuring robust defense against exploitation techniques described in MITRE ATT&CK framework related to unauthorized data collection via local privilege escalation vectors like T1057 Process Discovery or T1082 System Information Discovery when combined with other vulnerabilities that allow code execution within the driver context.
Mitigation strategies for this issue primarily involve applying the upstream kernel patch provided by the Linux maintainers, which corrects the comparison operator in btintel_pcie_msix_tx_handle. Systems running affected versions of the Linux kernel should update to a version where this fix is included. For environments unable to immediately upgrade, monitoring Bluetooth subsystem logs for unexpected crashes or anomalies during high-throughput transmission scenarios may help detect potential exploitation attempts. Additionally, enforcing strict memory protection mechanisms such as Kernel Page Table Isolation and enabling stack canaries can reduce the likelihood of successful exploitation by limiting the impact of any out-of-bounds access that might still occur due to other latent vulnerabilities in adjacent code paths.