CVE-2026-89621 Linux CVE debrief

Who should care

Linux system administrators and users with USB devices connected to their systems should assess their exposure and apply the kernel patch if necessary. The vulnerability affects Linux systems with HID mcp2221 drivers, potentially allowing attackers to exploit the vulnerability and leak sensitive information. System administrators should review system configurations, verify kernel patch application, and monitor USB device activity for potential malicious  

Why it matters

This vulnerability in the Linux kernel's HID mcp2221 driver allows malicious USB devices to potentially leak kernel memory, increasing the risk of system compromise. Linux system administrators and users should assess their exposure, apply the kernel patch, and verify system configurations.

• Potential information disclosure through leaked kernel memory
• Increased risk of system compromise through malicious USB devices
• Need for kernel patching and system updates
• Verification of system configurations and inventory required

Technical summary

The Linux kernel's HID mcp2221 driver did not validate the size of incoming HID reports, allowing a malicious USB device to cause the kernel to leak uninitialized memory. A size check has been added to prevent this issue. The vulnerability affects Linux systems with HID mcp2221 drivers, potentially allowing attackers to exploit the vulnerability and leak sensitive information. The patch adds a minimum size check at entry and validates that the source range fits within the received report before the copy, preventing the leak of uninitialized kernel memory.

Defensive priority

Medium

Recommended defensive actions

• Review and apply the kernel patch to ensure the HID mcp2221 driver is updated
• Monitor USB device activity for potential malicious behavior
• Verify system configurations and inventory for affected Linux kernel versions
• Review compensating controls for exposed systems while remediation is scheduled and verified
• Check relevant monitoring, detection, and logs for exposed assets that need extra review
• Track exceptions, retest remediated assets, and close the item only after evidence is documented
• Confirm whether affected product deployments exist in managed environments and assign an owner for follow-up

Evidence notes

The CVE record and NVD entry provide details on the vulnerability, but additional information on affected systems and exploitation is limited. The Linux kernel's HID mcp2221 driver did not validate the size of incoming HID reports, allowing a malicious USB device to cause the kernel to leak uninitialized memory. The vulnerability has been resolved with an added size check. However, the exact scope of affected systems and potential exploitation attempts remain unclear. Defenders should verify system configurations, review kernel patch

Sources and references

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.