CVE-2026-98893 in Linux
Summary
by MITRE • 10/23/2026
In the Linux kernel, the following vulnerability has been resolved:
firmware: arm_scmi: Validate SENSOR_UPDATE payload size
SENSOR_UPDATE carries one or more sensor readings after the fixed notification header. The parser derives the expected reading count from the sensor description, but it did not verify that the received payload contains those entries before parsing them.
Reject truncated update notifications before reading the variable array.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 10/23/2026
The Linux kernel firmware subsystem for ARM System Control and Management Interface (SCMI) has addressed a critical input validation flaw within the SENSOR_UPDATE notification handler. This vulnerability stems from an insufficient verification of payload boundaries, specifically regarding the length of data received in sensor update notifications. The SCMI protocol defines specific message structures where SENSOR_UPDATE messages contain a fixed header followed by one or more variable-length sensor readings. While the kernel parser correctly calculates the expected number of reading entries based on the predefined sensor description metadata, it previously failed to verify that the actual incoming payload contained sufficient data to satisfy this expectation before attempting to parse and access these array elements.
This oversight creates a classic out-of-bounds read condition, which falls under CWE-125: Out-of-bounds Read in standard vulnerability classification taxonomies. When a truncated or malformed SENSOR_UPDATE message is received from the firmware, the kernel proceeds to dereference pointers into memory regions that may not contain valid data or may lie outside the allocated buffer boundaries. Because the parser does not check if the remaining payload size matches the calculated requirement for the expected number of readings, it risks reading arbitrary memory contents. In severe cases, this can lead to information disclosure where sensitive kernel memory is leaked to user space or firmware contexts that have access to these parsed values.
From an operational perspective, the impact of this vulnerability extends beyond simple data corruption. An attacker with the ability to influence or intercept SCMI messages from the system firmware could craft maliciously sized SENSOR_UPDATE packets. By sending payloads shorter than expected, the kernel might read uninitialized memory or adjacent structures, potentially leading to unpredictable behavior including kernel panics, denial of service conditions due to page faults, or more sophisticated exploitation vectors if the leaked data aids in further attacks against the host system. This is particularly concerning given that SCMI interfaces are often exposed through device drivers and sysfs entries accessible by local users with appropriate privileges.
The remediation involves enforcing strict length checks before processing the variable array of sensor readings. The updated code now validates that the received payload size is at least equal to the sum of the fixed header size and the expected byte count for all declared sensor readings. If the payload is truncated, the notification is rejected immediately without attempting to parse individual reading entries. This defensive programming approach ensures memory safety by preventing access beyond the allocated buffer limits.
Security practitioners should ensure that systems running affected Linux kernel versions are updated to a patched release where this validation logic has been implemented. Additionally, organizations relying on SCMI-based firmware interactions should review their device driver implementations for any custom parsing logic that might bypass standard framework protections. Monitoring logs for unexpected rejection of sensor update notifications can also serve as an indicator of potential exploitation attempts targeting this specific input validation weakness. This fix aligns with broader industry efforts to harden kernel interfaces against malformed inputs, reinforcing the principle of least privilege and strict boundary verification in system-level software components.