CVE-2026-98830 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
wifi: wfx: validate MIB read length before copying to caller
wfx_hif_read_mib() copies reply->length bytes from the firmware response into the caller-provided buffer without checking that reply->length does not exceed val_len. A firmware response with a length field larger than expected overruns the caller buffer and reads past the end of the reply allocation.
Replace the dead -ENOMEM check with an active validation that reply->length fits within val_len before the memcpy.
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Analysis
by VulDB Data Team • 10/18/2026
The vulnerability identified in the Linux kernel's wireless driver subsystem, specifically within the wfx_hif_read_mib function, represents a critical buffer overflow risk stemming from insufficient input validation of data lengths received from firmware. This component is responsible for reading Management Information Base (MIB) structures which are essential for configuring and monitoring Wi-Fi device parameters such as channel settings, security policies, and connection statistics. The core technical flaw lies in the absence of bounds checking before a memory copy operation occurs. When the driver requests MIB data from the firmware via the Host Interface (HIF), it receives a response structure that includes a length field indicating how many bytes are present in the payload. However, the existing implementation blindly trusts this value and proceeds to execute a memcpy operation using reply->length as the source size without verifying whether this amount fits within the destination buffer provided by the caller, referred to here as val_len.
This lack of validation creates two distinct but related security issues depending on the state of the memory buffers involved. First, if the length specified in the firmware response exceeds the allocated space in the caller's buffer (val_len), a heap-based or stack-based buffer overflow occurs. This allows an attacker who can influence the firmware response to overwrite adjacent memory structures, potentially leading to arbitrary code execution with kernel privileges. Second, and equally dangerous given the specific description provided, if reply->length is larger than expected but within some broader allocation boundary that includes data beyond the intended MIB payload, the driver reads past the end of the valid reply allocation. This constitutes an out-of-bounds read vulnerability where sensitive memory contents from other kernel structures or potentially user-space data mapped into kernel space are exposed to the wireless driver context.
From a classification perspective, this flaw aligns with CWE-120 Buffer Copy without Checking Size of Input and CWE-134 Use of Externally-Controlled Format String if format strings were involved, though primarily it is a classic buffer overflow scenario categorized under CWE-787 Out-of-bounds Write when the destination buffer is exceeded. In terms of attack vectors, this vulnerability could be exploited through local privilege escalation or potentially remote exploitation depending on how easily an attacker can trigger specific MIB read operations and manipulate firmware responses. The MITRE ATT&CK framework maps this behavior to techniques involving memory corruption for initial access or defense evasion, specifically under the category of Exploitation for Privilege Escalation if used by a local user with limited privileges to gain higher system control.
The operational impact of this vulnerability is severe due to its location in the kernel space and the high privilege level required to interact with wireless device drivers. Successful exploitation could allow an unprivileged local user to crash the system, causing a denial of service through kernel panic or memory corruption that destabilizes critical subsystems. More critically, it enables arbitrary code execution within the kernel context, granting full control over the operating system including access to all data stored on disk, ability to install rootkits, and bypassing security mechanisms like SELinux or AppArmor. The presence of a dead -ENOMEM check in the original code suggests that error handling was present but not effectively applied to this specific boundary condition, indicating a lapse in defensive programming practices where potential failure modes were acknowledged but not actively mitigated through validation logic.
To mitigate this vulnerability, developers must implement strict bounds checking prior to any memory copy operations involving external data sources such as firmware responses. The fix involves replacing the ineffective error handling with an active validation step that compares reply->length against val_len and aborts the operation if the former exceeds the latter. This ensures that no more bytes are copied than what was explicitly allocated by the caller, thereby preventing both buffer overflows and out-of-bounds reads. Additionally, adopting static analysis tools during development can help identify similar patterns where length fields from external inputs are used directly in memory operations without verification. Regular auditing of driver code for proper input validation is essential to maintain the integrity of kernel-space applications that interface with hardware components whose behavior may be unpredictable or maliciously manipulated.