CVE-2026-89627 Overview
CVE-2026-89627 is a memory leak vulnerability in the Linux kernel's HID (Human Interface Device) roccat driver. The flaw resides in how the driver manages buffered device reports during device destruction. The roccat_report_event() function duplicates each incoming report using kmemdup() and stores the allocation in a circular buffer slot, but device teardown paths free the struct roccat_device without releasing any reports still held in cbuf[]. This leaks up to ROCCAT_CBUF_SIZE report buffers per device instance. The vulnerability has been resolved by adding a destructor that frees every buffered report before freeing the device structure.
Critical Impact
Repeated attach/detach cycles of Roccat HID devices leak kernel memory, degrading system stability over time on affected Linux kernels.
Affected Products
- Linux kernel (mainline and stable branches containing the HID roccat driver)
- Distributions shipping kernels prior to the fixes referenced in the upstream stable commits
- Systems interacting with Roccat-branded HID peripherals
Discovery Timeline
- 2026-09-11 - CVE-2026-89627 published to NVD
- 2026-09-14 - Last updated in NVD database
Technical Details for CVE-2026-89627
Vulnerability Analysis
The Linux HID roccat driver buffers device reports so that userspace consumers can read them through a character device interface. Each report received by roccat_report_event() is duplicated with kmemdup(), and the resulting pointer is placed into a slot in a per-device circular buffer named cbuf[]. Allocations are released only when a given slot is overwritten by a newer report.
When the device is destroyed, the driver frees struct roccat_device directly. Any reports still residing in cbuf[] slots that were never overwritten remain allocated but no longer reachable through any pointer. This constitutes a kernel-side memory leak [CWE-401]. The severity remains bounded because the leak size per device is limited to ROCCAT_CBUF_SIZE entries, but repeated device destruction paths compound the loss.
Root Cause
The root cause is missing cleanup logic in the destruction paths for registered Roccat devices. The lifecycle of report allocations was tied only to slot reuse in the circular buffer, not to the lifecycle of the parent device. When the device object is torn down, the pending slot contents are orphaned. The upstream fix introduces a small destructor that iterates through cbuf[], frees each remaining report, and is invoked from both destruction paths.
Attack Vector
Triggering the leak requires a Roccat HID device to be attached, receive events that populate cbuf[], and then be destroyed before those slots are overwritten. Repeated USB attach/detach sequences, whether from physical device hot-plugging or from a malicious USB device that emulates Roccat identifiers, can exercise the leaking path multiple times. There is no evidence of remote exploitation, and the primary impact is progressive exhaustion of kernel memory rather than code execution.
No public proof-of-concept code has been published for this issue. See the upstream commits referenced under Patch Information for the exact code changes.
Detection Methods for CVE-2026-89627
Indicators of Compromise
- Growing kernel Slab or SUnreclaim counters in /proc/meminfo on hosts that frequently connect and disconnect Roccat HID peripherals
- KMEMLEAK reports referencing allocations originating from roccat_report_event() and kmemdup() call sites in the hid-roccat module
- Repeated USB bind/unbind events for devices identified with Roccat vendor identifiers in kernel logs
Detection Strategies
- Enable CONFIG_DEBUG_KMEMLEAK in test environments and monitor /sys/kernel/debug/kmemleak for allocations tied to the hid-roccat driver
- Track kernel memory growth over time on endpoints that interact with HID peripherals, correlating with udev device events
- Audit installed kernel package versions against the upstream stable commits listed in the vendor advisories
Monitoring Recommendations
- Collect dmesg and journald entries for HID subsystem events and forward them to a centralized logging pipeline
- Alert on abnormal Slab memory growth on Linux endpoints and workstations that use gaming peripherals
- Include kernel version telemetry in endpoint inventory to identify hosts still running unpatched kernels
How to Mitigate CVE-2026-89627
Immediate Actions Required
- Update affected Linux systems to a kernel version that includes the upstream fix commits for the hid-roccat driver
- Restrict physical and USB access on multi-user or shared systems where untrusted HID peripherals could be attached
- Reboot long-running hosts that exhibit unexplained kernel memory growth after applying the update
Patch Information
The fix has been merged into the Linux kernel across multiple stable branches. Refer to the following upstream commits for the exact code changes: Linux Kernel Commit 4cb3ff3, Linux Kernel Commit 690da91, Linux Kernel Commit 943b8dc, Linux Kernel Commit b3cc411, Linux Kernel Commit bbff0cc, Linux Kernel Commit cebb20b, Linux Kernel Commit da00eac, and Linux Kernel Commit fbb5a60. Apply your distribution's kernel update once it incorporates one of these commits.
Workarounds
- Blacklist the hid-roccat kernel module on systems that do not require Roccat peripheral support until the kernel can be patched
- Avoid frequent hot-plug cycles of Roccat HID devices on unpatched kernels to reduce accumulation of leaked report buffers
- Use USB access control policies, such as usbguard, to prevent unapproved HID devices from binding to the driver
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.