CVE-2026-81017 Overview
CVE-2026-81017 is an out-of-bounds read and write vulnerability in the Linux kernel's ChromeOS platform/chrome sensorhub driver. The flaw resides in cros_ec_sensor_ring_process_event(), which uses an 8-bit sensor number reported by the Embedded Controller (EC) to index the sensorhub->batch_state[] array. The ring handler validates FIFO event count, per-read count, and ring bounds, but does not validate in->sensor_num against the allocated sensorhub->sensor_num entries. A crafted or malformed sensor number equal to or larger than sensor_num triggers memory access beyond the allocated buffer.
Critical Impact
A local attacker with control over EC FIFO event data can trigger kernel out-of-bounds reads and writes, potentially leading to memory corruption, information disclosure, or privilege escalation on affected ChromeOS-based Linux systems.
Affected Products
- Linux kernel builds including the platform/chrome sensorhub driver (cros_ec_sensorhub)
- ChromeOS devices leveraging the Embedded Controller sensor FIFO interface
- Distributions shipping vulnerable kernel versions prior to the referenced stable commits
Discovery Timeline
- 2026-09-11 - CVE-2026-81017 published to NVD
- 2026-09-14 - Last updated in NVD database
Technical Details for CVE-2026-81017
Vulnerability Analysis
The defect lives in the ChromeOS sensorhub ring event pipeline. Each EC FIFO event includes an 8-bit sensor_num field. The function cros_ec_sensorhub_ring_handler() validates structural fields such as event counts and ring bounds. It does not, however, verify that in->sensor_num falls within the range allocated for sensorhub->batch_state[].
When cros_ec_sensor_ring_process_event() runs, it uses sensor_num directly as an array index. Any value greater than or equal to sensorhub->sensor_num results in out-of-bounds memory access. Because the driver both reads from and writes to batch_state[] using this index, the flaw enables both information disclosure and controlled kernel memory corruption. The local attack vector with no privileges required means any user-mode context able to influence EC-reported events can trigger the condition.
Root Cause
The root cause is missing input validation on attacker-influenced data crossing a trust boundary. The driver treats the EC as a trusted source and passes the sensor number to array indexing without bounds checking. This is an Out-of-Bounds Read and Out-of-Bounds Write class defect stemming from improper validation of external input used as an index.
Attack Vector
Exploitation requires local access on a system running the vulnerable cros_ec_sensorhub driver. An adversary capable of injecting or manipulating EC FIFO events supplies a sensor_num value equal to or greater than the allocated batch_state[] size. The kernel then dereferences memory outside the allocated array on subsequent event processing. Repeated exploitation can be used to corrupt adjacent kernel structures or leak sensitive kernel memory contents.
No verified public proof-of-concept code is available. Technical details of the fix are documented in the upstream stable tree commits referenced by this CVE, including Kernel Commit 2b602ecf and Kernel Commit 324880f9.
Detection Methods for CVE-2026-81017
Indicators of Compromise
- Unexpected kernel oops, KASAN reports, or panics referencing cros_ec_sensor_ring_process_event or cros_ec_sensorhub_ring_handler
- Kernel logs showing dropped or malformed EC FIFO events after patch application
- Anomalous sensor telemetry patterns from EC-connected devices preceding kernel instability
Detection Strategies
- Enable KASAN (Kernel Address Sanitizer) in test and staging kernels to surface out-of-bounds accesses in the sensorhub ring path
- Audit installed kernel packages against the fixed commits listed by the upstream Linux stable tree for this CVE
- Correlate kernel crash telemetry with process activity that interacts with /dev/cros_ec or related sensor interfaces
Monitoring Recommendations
- Forward kernel ring-buffer logs (dmesg, journald) to a central logging platform for pattern-based alerting on sensorhub driver faults
- Monitor for unexpected reboots or kernel warnings on ChromeOS-derived Linux fleets
- Track kernel version inventory to confirm coverage of the stable release containing the fix
How to Mitigate CVE-2026-81017
Immediate Actions Required
- Update affected Linux kernels to a stable release containing the fix commits referenced by this CVE
- Prioritize devices that expose the cros_ec_sensorhub driver, including ChromeOS-derived Linux systems and hardware with Google EC firmware
- Restrict local access to systems that cannot be immediately patched, since the vulnerability requires local privileges of the attack surface
Patch Information
The upstream fix validates in->sensor_num inside the ring handler and drops malformed events before they reach cros_ec_sensor_ring_process_event(). Patches are available across multiple stable branches. Reference commits include Kernel Commit 3a76b87e, Kernel Commit 3d2636dc, Kernel Commit 4d9bf63e, Kernel Commit 5eaf7faa, Kernel Commit 833740a2, and Kernel Commit d1b4add6. Apply the appropriate patch matching the deployed kernel branch.
Workarounds
- Unload or blacklist the cros_ec_sensorhub module on systems where sensor telemetry is not required
- Limit local user access and enforce least-privilege policies to reduce exposure of the local attack surface
- Deploy kernel lockdown or module-loading restrictions on production systems to reduce the ability of local actors to interact with vulnerable drivers
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
