CVE-2026-98247 in Linux
Summary
by MITRE • 10/06/2026
In the Linux kernel, the following vulnerability has been resolved:
Bluetooth: hci_codec: validate vendor codec count length
The Read Local Supported Codecs parsers consume the variable-sized standard codec array before parsing the vendor codec count. Although the initial reply-size check includes a vendor count byte in the fixed layout, it does not guarantee that the byte remains after the standard codec array.
If a controller reply ends immediately after that array, calculating the vendor codec array size reads vnd_codecs->num beyond the skb data. Use skb_pull_data() to validate and consume each codec header before using its count in both command variants.
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Analysis
by VulDB Data Team • 10/06/2026
The Linux kernel Bluetooth subsystem contains a critical input validation flaw within the HCI codec parsing logic, specifically affecting the handling of vendor-specific audio codecs. This vulnerability arises from an improper boundary check during the processing of Read Local Supported Codecs responses. The parser is designed to first consume a variable-sized array of standard codec identifiers before attempting to parse the subsequent vendor codec count and associated data structures. While the initial reply-size validation includes the byte for the vendor count in its fixed layout calculation, it fails to account for the dynamic length of the preceding standard codec array. Consequently, if a Bluetooth controller returns a response where the payload ends immediately after the standard codec array, the parser proceeds without verifying that sufficient data remains available for the subsequent operations.
This architectural oversight leads to an out-of-bounds read condition when the system attempts to access vendor-specific information. Specifically, the code calculates the size of the vendor codec array by reading a value beyond the allocated socket buffer (skb) data boundaries. By accessing memory outside the valid range of the received packet, the kernel risks exposing sensitive internal state or causing undefined behavior depending on what follows the packet in memory. This type of error is characteristic of improper input validation where dynamic lengths are not correctly bounded against total available payload size before access occurs. The flaw exists in both command variants that handle local supported codec queries, making it a persistent issue across different interaction modes within the Bluetooth stack.
From an operational perspective, this vulnerability can lead to kernel instability or potential information disclosure. An out-of-bounds read allows an attacker with proximity to the device's Bluetooth interface to potentially leak kernel memory contents into user space through subsequent processing of corrupted data structures. While exploitation for arbitrary code execution is less likely given that this is a read operation rather than a write, the exposure of internal kernel pointers or sensitive configuration details can aid in further attacks such as bypassing address space layout randomization (ASLR). The impact extends to system reliability as well, since accessing invalid memory regions may trigger page faults or panic conditions, resulting in a denial of service for Bluetooth functionality and potentially crashing the host system if not handled gracefully by lower-level error traps.
The remediation involves rigorous validation of data boundaries before consumption. The fix implements the use of skb_pull_data() to validate and consume each codec header sequentially. This ensures that the parser only proceeds to read vendor-specific counts when it is mathematically guaranteed that those bytes exist within the packet buffer. By validating the length at each step rather than relying on a static initial check, the kernel prevents access beyond the allocated memory space. This approach aligns with secure coding practices that emphasize defensive parsing of variable-length fields in network protocols.
This vulnerability maps to CWE-125, which describes Out-of-bounds Read, as it involves accessing data outside the intended buffer boundary due to insufficient validation of input lengths. In terms of attack vectors and techniques, this flaw relates to ATT&CK technique T1083, File and Directory Discovery, if exploited for information leakage, or more broadly to improper input handling that facilitates reconnaissance activities against the host system. Security practitioners should ensure that systems running affected Linux kernel versions are updated immediately to patch these parsing routines. Additionally, network-level monitoring can be employed to detect anomalous Bluetooth HCI traffic patterns that might indicate probing attempts targeting this specific parsing logic in vulnerable implementations.