CVE-2026-98819 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: btintel: validate DDC record lengths
Parse DDC record lengths in unsigned storage so 0xFF does not wrap. Reject records smaller than the mandatory three-byte header, records exceeding U8_MAX, and records exceeding remaining firmware bytes before issuing Intel_Write_DDC.
This issue was reported by Claude Mythos.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 10/19/2026
The Linux kernel Bluetooth subsystem contains a critical integer handling flaw within the Intel wireless driver component known as btintel. This vulnerability arises from improper validation of Dynamic Data Container (DDC) record lengths during firmware parsing operations. The core technical deficiency lies in the data type used to store and process these length values. Specifically, the code previously failed to ensure that DDC record lengths were parsed into an unsigned storage format capable of correctly interpreting byte values up to their maximum limit without unintended arithmetic behavior. This oversight creates a scenario where specific input values can trigger integer wraparound or misinterpretation issues, particularly when dealing with boundary conditions such as the value 0xFF which represents 255 in decimal but may be mishandled if not strictly constrained within an appropriate unsigned eight-bit integer context during validation logic.
The operational impact of this vulnerability is significant because it affects the integrity and safety of firmware updates sent to Intel Bluetooth hardware. When the kernel parses DDC records, it prepares data structures that are subsequently written to the device via the Intel_Write_DDC command. If a record length is not validated correctly against the available remaining firmware bytes or if small invalid headers are accepted, the driver may attempt to write malformed or out-of-bounds data to the hardware interface. This can lead to buffer overflows, memory corruption within the kernel space, or undefined behavior in the Bluetooth controller itself. Such conditions could potentially be exploited by a local attacker with access to Bluetooth interfaces or firmware update mechanisms to cause a denial of service through system crashes, or in more complex scenarios, achieve arbitrary code execution if the corrupted data can influence subsequent control flow paths in the driver stack.
This flaw is categorized under CWE-190: Integer Overflow or Wraparound and CWE-20: Improper Input Validation within standard vulnerability classification frameworks. From a tactical perspective related to the MITRE ATT&CK framework, this type of issue facilitates exploitation vectors associated with Local Privilege Escalation (T1068) if an attacker can trigger the vulnerable code path through local Bluetooth interactions or firmware injection attacks. The failure to validate input against expected bounds allows for potential memory safety violations that are foundational to many kernel-level exploits.
To mitigate this vulnerability, it is essential to enforce strict type checking and boundary validation during the parsing phase of DDC records. Developers must ensure that record lengths are stored in unsigned variables that accurately reflect their magnitude without wraparound risks. Validation logic should explicitly reject any record smaller than the mandatory three-byte header size, as these are structurally invalid for Intel firmware formats. Furthermore, the system must verify that each record length does not exceed U8_MAX (255) and critically, ensure that the cumulative or individual record lengths do not surpass the remaining bytes available in the firmware image before issuing the write command. This ensures that no out-of-bounds memory access occurs during the transfer of data to the hardware device. Regular code audits focusing on integer arithmetic safety and input validation boundaries are recommended for all kernel drivers interacting with external peripherals to prevent similar classes of vulnerabilities from being introduced or persisting in the codebase.