CVE-2026-98481 in Linux
Summary
by MITRE • 10/18/2026
In the Linux kernel, the following vulnerability has been resolved:
nfc: port100: reject frames whose declared length exceeds the received data
port100_recv_response() passes the URB transfer buffer to port100_rx_frame_is_valid(), which checksums le16_to_cpu(frame->datalen) bytes of frame->data. datalen is a 16-bit field supplied by the device and is never checked against the number of bytes actually received (urb->actual_length), so a device reporting a datalen larger than the received frame makes port100_data_checksum() read out of bounds past the transfer buffer.
Reject a response whose declared frame size does not fit the received length before validating it.
Found by 0sec (https://0sec.ai) using automated source analysis; the missing bound is evident from source. Compile-tested.
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Analysis
by VulDB Data Team • 10/18/2026
The Linux kernel's Near Field Communication subsystem contains a critical out-of-bounds read vulnerability within the port100 NFC driver, specifically in the function responsible for handling incoming response frames. This flaw arises from an insufficient validation of data length fields provided by external hardware devices. When the device sends a frame to the host system via USB, it includes a datalen field that indicates the expected size of the payload contained within the transfer buffer. The kernel code retrieves this value and passes the entire URB (USB Request Block) transfer buffer to a validation function named port100_rx_frame_is_valid. Inside this function, the driver attempts to compute a checksum over the data by reading le16_to_cpu(frame->datalen) bytes from frame->data. However, there is no prior check comparing this declared datalen against urb->actual_length, which represents the true number of bytes actually received and available in the buffer during that specific transfer event.
This lack of boundary checking creates a direct path for an out-of-bounds read condition classified under CWE-125: Out-of-bounds Read. If a malicious or compromised NFC device reports a datalen value larger than the actual amount of data transferred, the checksum calculation routine will attempt to access memory locations beyond the end of the allocated transfer buffer. While this specific instance is an out-of-bounds read rather than a write, it still poses significant security risks including information disclosure and potential denial of service through kernel panics or undefined behavior depending on what lies in the adjacent memory space. The vulnerability highlights a common class of errors where trust is placed in external inputs without verifying them against actual resource constraints such as buffer sizes or transfer lengths.
From an operational perspective, this vulnerability allows for local exploitation if an attacker has physical access to the NFC interface and can manipulate the device firmware or hardware behavior to send malformed frames with inflated length fields. Although the impact may be limited by the fact that it is a read operation rather than a write, reading kernel memory can leak sensitive information such as stack pointers, heap metadata, or other process data into user space if subsequent operations utilize these corrupted values. Furthermore, accessing invalid memory regions often triggers page faults or general protection faults within the kernel, leading to system instability and service disruption for NFC-dependent applications. This aligns with ATT&CK technique T1083: File and Directory Discovery in contexts where such leaks facilitate further reconnaissance, though primarily it represents a stability issue exploitable via physical proximity attacks.
The resolution involves modifying the port100_recv_response function to enforce strict length validation before any data processing occurs. Specifically, the driver must now compare the declared datalen against urb->actual_length and reject any response where the claimed size exceeds the actual received bytes. This simple check ensures that subsequent operations like checksumming remain within valid memory boundaries. The fix was identified through automated source code analysis by 0sec, demonstrating the value of static application security testing in detecting missing boundary checks early in the development lifecycle. To mitigate similar risks across other drivers and subsystems, developers should consistently validate all external length fields against actual buffer capacities before performing any read or write operations on those buffers. System administrators can apply kernel updates that include this patch to restore secure operation of NFC interfaces while maintaining compliance with standard security practices for input validation.