CVE-2026-98575 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
nfc: pn533: fix OOB read in pn533_acr122_is_rx_frame_valid()
frame->ccid.datalen is read directly from the USB response frame and used, unchecked, as an index into frame->data[]. A malicious or
malfunctioning device can set this field to an arbitrary value, causing the driver to read far outside the received buffer.
Bound ccid.datalen against the maximum possible ACR122 frame size before using it. This replaces the existing datalen == 0 check, since datalen < 2 already covers that case and additionally rejects datalen == 1, which would still underflow the "datalen - 2" offset used below.
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Analysis
by VulDB Data Team • 10/18/2026
The vulnerability identified in the Linux kernel's Near Field Communication subsystem specifically affects the pn533 driver when interacting with ACR122 devices. This flaw manifests as an out-of-bounds read within the function pn533_acr122_is_rx_frame_valid, which is responsible for validating incoming data frames from connected NFC hardware. The core technical issue stems from a failure to properly validate input data received over USB before it is processed by the driver logic. Specifically, the variable frame->ccid.datalen is extracted directly from the USB response frame sent by the external device and used immediately as an index into the frame->data array without any prior bounds checking or sanitization. This design oversight assumes that the hardware will always provide well-formed data with lengths consistent with expected protocol specifications, a assumption that does not hold in security-conscious threat models where peripheral devices may be compromised or maliciously modified.
From a technical perspective, this vulnerability allows for an out-of-bounds read operation because the driver accesses memory locations based on user-controlled input from the hardware interface. When a device sets datalen to an arbitrary value significantly larger than the allocated buffer size, the kernel attempts to access memory beyond the bounds of frame->data. This can lead to information disclosure if the accessed memory contains sensitive data such as cryptographic keys or other process-specific information that leaks into the NFC subsystem's output buffers. Furthermore, depending on how this invalid read interacts with subsequent code paths and compiler optimizations, it could potentially trigger undefined behavior, leading to kernel panics or stability issues. The vulnerability is classified under CWE-125, which covers Out-of-bounds Read vulnerabilities where software reads data past the end of a buffer.
The operational impact of this flaw extends beyond simple memory corruption risks. An attacker with physical access to an NFC reader port could exploit this by connecting a malicious device that sends crafted USB frames with excessively large datalen fields. This exploitation vector aligns with ATT&CK techniques related to peripheral device manipulation and local privilege escalation if the kernel crash or information leak can be leveraged further within the system context. The lack of input validation on hardware interfaces represents a significant security gap, as many developers assume physical proximity implies trustworthiness, which is increasingly recognized as an incorrect assumption in modern threat landscapes involving supply chain attacks or compromised peripherals.
To mitigate this vulnerability, the Linux kernel maintainers have implemented a fix that enforces strict bounds checking on the datalen field before it is used for array indexing. The solution involves validating that ccid.datalen does not exceed the maximum possible frame size defined by the ACR122 protocol specification. This approach replaces the previous insufficient check, which only verified if datalen was equal to zero. The new logic ensures that any value less than two is rejected, addressing a secondary issue where smaller values could still cause underflow in subsequent calculations involving offsets like datalen minus two. By capping the accepted length and rejecting invalid ranges early in the processing pipeline, the driver prevents access to unauthorized memory regions. System administrators should ensure their systems are updated with kernel patches that include this fix to maintain integrity against malicious NFC devices or malfunctioning hardware components.