CVE-2026-80759 in Linux
Summary
by MITRE • 09/04/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_aml: validate firmware segment lengths
aml_download_firmware() reads two lengths from the firmware header and uses them to build pointers before checking that the header and segment data are present. A truncated or inconsistent firmware image can make the driver read past firmware->data while constructing TCI commands.
Reject images shorter than the header and ensure that the ICCM and DCCM ranges fit within the loaded firmware before downloading either segment.
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Analysis
by VulDB Data Team • 09/04/2026
The Linux kernel Bluetooth subsystem contains a critical input validation flaw within the Atheros HCI driver, specifically in the function responsible for downloading firmware to the hardware device. This vulnerability arises from an improper sequence of operations where pointer arithmetic is performed on data structures derived directly from untrusted external inputs before those inputs are validated for integrity and bounds. The core issue lies in how the driver processes binary firmware images provided by userspace or loaded via system interfaces, which represent a common attack surface for kernel exploitation if not handled with strict defensive programming practices.
The technical flaw centers on the function aml_download_firmware(), which parses headers from incoming firmware blobs to determine segment lengths and memory addresses. In the vulnerable implementation, the driver extracts length fields and calculates pointer offsets based on these values immediately upon receipt of the header data. This calculation occurs prior to any verification that the actual buffer contains sufficient bytes to support those calculated ranges. Consequently, if a malicious or corrupted firmware image is provided with truncated headers or inconsistent segment lengths, the resulting pointers may reference memory locations beyond the allocated bounds of the firmware->data buffer.
This out-of-bounds read condition allows an attacker who can supply arbitrary firmware images to trigger reads from kernel memory regions outside the intended scope. Depending on the specific layout of kernel memory and the values contained in the malformed header, this could lead to information disclosure where sensitive kernel data is leaked through subsequent operations that utilize these invalid pointers. Furthermore, if the driver attempts to process or transmit commands constructed using these corrupted pointers, it may result in undefined behavior, potentially leading to a denial of service condition characterized by system instability or a kernel panic due to accessing unmapped memory pages.
The operational impact of this vulnerability is significant because firmware loading often requires elevated privileges but can sometimes be influenced through less privileged interfaces depending on the specific device configuration and access controls. An attacker with local access could craft a specially crafted binary file that, when processed by the Bluetooth stack, causes the kernel to read arbitrary memory contents. This aligns with CWE-125, Out-of-bounds Read, as it involves accessing memory beyond the intended buffer boundary. Additionally, because this vulnerability facilitates unauthorized data retrieval from the kernel space, it relates closely to CWE-200, Information Exposure, and potentially CWE-787 if the out-of-bounds access leads to a crash that disrupts system availability.
From an offensive security perspective, such vulnerabilities are often leveraged in conjunction with other flaws to achieve privilege escalation or persistent access within compromised systems. The ATT&CK framework categorizes this type of behavior under techniques involving exploitation for data exfiltration or disruption of service. Specifically, the ability to read kernel memory can be used to gather credentials or cryptographic keys stored in adjacent memory regions, facilitating further lateral movement or deeper compromise of the host system.
To mitigate this vulnerability, developers have implemented strict validation checks that ensure the firmware image meets minimum size requirements before any pointer arithmetic is performed. The fix mandates rejecting images that are shorter than the expected header structure and verifies that both ICCM and DCCM memory ranges fall entirely within the bounds of the loaded firmware data. This defensive approach ensures that all subsequent operations rely on verified, safe offsets, thereby eliminating the possibility of out-of-bounds reads during the firmware download process. System administrators should ensure their Linux kernels are updated to include this patch, as it closes a critical gap in input validation for Bluetooth hardware drivers.