CVE-2026-98711 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
wifi: cw1200: fix TX padding OOB read leaking heap data to device
The TX path rounds the transfer size up to the bus alignment (align_size(), up to 511 bytes for SDIO, 1 byte for SPI) but sends the padded length straight from the frame buffer, which has no room reserved for the padding. cw1200_data_write() therefore reads past the end of the frame and the bus transfer carries those bytes to the device. A bogus device can collect up to 511 bytes of kernel heap data per TX frame.
The RX path does not have this problem: it allocates the skb with the aligned length (alloc_len) before reading.
Compute the exact padding with the bus align_size() callback, make sure queued TX frames have tailroom for it, and zero the padding bytes before the transfer so nothing past the frame is exposed.
This is not expected to change driver behavior on most cases: frame contents and transfer sizes are unchanged, only the content of the padding bytes (previously undefined stale memory, now zero), which the device never reads since the WSM header carries the real frame length. The skb expansion can only fail under memory exhaustion, in which case the frame is dropped like on the existing error paths of cw1200_tx().
Discovered by Atuin - Automated Vulnerability Discovery Engine.
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Analysis
by VulDB Data Team • 10/19/2026
The Linux kernel driver for the CW1200 wireless interface contains a critical out-of-bounds read vulnerability within its transmission path that results in the leakage of sensitive kernel heap data to external hardware devices. This flaw stems from an implementation error where the driver rounds up the transfer size to meet bus alignment requirements, which can be as high as 511 bytes for SDIO interfaces or one byte for SPI connections. However, while the calculated padded length is used to initiate the bus transfer, the actual memory buffer being read does not contain reserved space for this additional padding. Consequently, when the driver writes data to the device, it reads past the end of the allocated frame buffer into adjacent kernel heap memory. This behavior allows a malicious or compromised device connected via SDIO or SPI to capture up to 511 bytes of uninitialized kernel heap data per transmitted frame, potentially exposing cryptographic keys, session tokens, or other sensitive information stored in that memory region.
This vulnerability is classified under CWE-125, which describes out-of-bounds read scenarios where software reads data past the end of a buffer. In terms of adversarial tactics, this flaw aligns with ATT&CK technique T1074, specifically Data Staged or Local Data Stealing, as it facilitates the exfiltration of information from the local system to an external entity through hardware interfaces. The root cause lies in the cw1200_data_write function, which fails to ensure that the socket buffer has sufficient tailroom for the required padding before performing the DMA transfer. While the receive path correctly allocates buffers with aligned lengths prior to reading data and is therefore unaffected, the transmit path's oversight creates a significant security gap. The device receives these extra bytes because the bus controller transfers exactly what is specified by the padded length, regardless of whether that memory belongs to the intended frame structure.
The operational impact of this vulnerability includes potential information disclosure attacks where an attacker with physical access or control over the wireless interface can extract kernel heap contents. Although the WSM header within each frame carries the actual valid frame length and theoretically prevents the device from interpreting the padding as meaningful data, the mere act of transferring uninitialized memory to a peripheral constitutes a severe security risk. The vulnerability was discovered using Atuin, an automated vulnerability discovery engine that identifies such logic errors in kernel drivers by analyzing memory access patterns during transmission operations.
To mitigate this issue, the driver implementation must be updated to compute the exact padding required based on the bus align_size callback and ensure that queued transmit frames have adequate tailroom allocated for it. Furthermore, before initiating any transfer, the padding bytes within the buffer should be explicitly zeroed out to prevent the exposure of stale heap data. This fix ensures that even if the device receives more bytes than intended due to alignment requirements, those extra bytes contain no sensitive information. The change is designed to maintain backward compatibility and not alter normal driver behavior under typical conditions; frame contents and transfer sizes remain unchanged for valid operations. In cases where memory exhaustion prevents the necessary skb expansion, the system will drop the frame consistent with existing error handling paths in cw1200_tx, thereby preserving stability while closing the security hole.