CVE-2026-96844 in Windows
Summary
by MITRE • 10/14/2026
Integer underflow (wrap or wraparound) in Microsoft Bluetooth Driver allows an authorized attacker to elevate privileges over an adjacent network.
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Analysis
by VulDB Data Team • 10/14/2026
The vulnerability identified involves a critical integer underflow flaw within the core components of the Microsoft Bluetooth driver stack, specifically affecting how memory buffers are allocated and processed during data parsing operations. This type of error typically occurs when a signed integer variable is decremented below zero or when an unsigned calculation results in a value that wraps around to a very large positive number due to insufficient bounds checking on input parameters provided by remote devices or local applications interacting with the Bluetooth subsystem. In this specific instance, the flaw allows for the manipulation of buffer sizes or loop counters such that the driver allocates less memory than required or accesses memory regions outside the intended boundaries, leading to potential heap corruption or arbitrary code execution contexts depending on the exact exploitation vector utilized by an attacker.
From a technical perspective, integer underflows are particularly dangerous in kernel-mode drivers because they often bypass standard security checks designed to prevent buffer overruns. When the driver fails to validate that a calculated size remains within valid positive bounds before passing it to memory allocation routines like ExAllocatePoolWithTag or similar internal functions, an attacker can craft malicious Bluetooth packets containing specially crafted header fields or payload structures. These malformed inputs trigger the underflow condition, causing the system to allocate a significantly smaller buffer than anticipated while still attempting to write data based on the original, larger logical size. This discrepancy results in writing beyond the allocated memory space, corrupting adjacent kernel objects, control flow handlers, or critical system state information stored in contiguous memory locations.
The operational impact of this vulnerability is severe due to its potential for privilege escalation over an adjacent network context. Although the description specifies that an authorized attacker is required, the term "adjacent network" implies proximity-based attack vectors such as Bluetooth Low Energy (BLE) advertisements or pairing requests which can often be initiated by devices within physical range without requiring explicit user authentication in many default configurations. If successfully exploited, this flaw allows a local unprivileged process or a nearby malicious device to execute arbitrary code with the high privileges of the SYSTEM account or kernel mode. This effectively compromises the integrity and confidentiality of the entire host system, enabling attackers to install malware, steal sensitive data, create backdoors, or pivot further into connected network segments that trust the compromised machine.
This vulnerability aligns closely with Common Weakness Enumeration (CWE) category CWE-192, which defines integer underflow wraparound errors, and is frequently associated with CWE-787, out-of-bounds write vulnerabilities resulting from incorrect size calculations. In terms of offensive security frameworks like MITRE ATT&CK, this flaw facilitates techniques related to Privilege Escalation via Exploitation of Local Vulnerabilities (T1068) and potentially Initial Access through Bluetooth-based attacks if the attacker is within range (T1539). The exploitation path typically involves crafting specific HCI commands or L2CAP packets that trigger the flawed parsing logic in the driver, leading to memory corruption that can be leveraged for kernel-level code execution.
Mitigation strategies must focus on both immediate patching and long-term architectural improvements. Organizations should immediately apply the latest security updates provided by Microsoft for their operating systems, as these patches typically include rigorous input validation checks and bounds verification logic within the Bluetooth driver source code to prevent integer underflows from occurring during buffer allocation. Additionally, administrators should disable unnecessary Bluetooth services on servers or critical infrastructure where physical proximity attacks are a concern, reducing the attack surface. For environments requiring persistent Bluetooth connectivity, implementing strict device whitelisting policies and ensuring that pairing modes do not allow unrestricted incoming connections can significantly reduce the risk of exploitation by limiting exposure to untrusted devices. Regular vulnerability scanning focused on driver integrity and memory safety issues should also be integrated into routine security operations to detect any potential misconfigurations or missing patches before they can be leveraged in an attack scenario.