CVE-2026-63906 Overview
CVE-2026-63906 is a use-after-free vulnerability in the Linux kernel's USB MUSB driver for the OMAP2430 platform. The flaw resides in the omap2430_probe() function, where of_node_put(np) is called prematurely before the last access to the device tree node np. When the node's reference count drops to zero, subsequent access dereferences freed memory. The issue affects the drivers/usb/musb/omap2430.c source file and has been patched across multiple stable kernel branches.
Critical Impact
A local attacker with the ability to trigger the vulnerable code path can achieve memory corruption in kernel space, potentially leading to privilege escalation, kernel information disclosure, or denial of service.
Affected Products
- Linux kernel builds including the USB MUSB omap2430 driver
- OMAP2430-based platforms using the mainline drivers/usb/musb/omap2430.c implementation
- Downstream distributions shipping unpatched stable kernel branches referenced in the fix commits
Discovery Timeline
- 2026-07-19 - CVE-2026-63906 published to NVD
- 2026-07-20 - Last updated in NVD database
Technical Details for CVE-2026-63906
Vulnerability Analysis
The vulnerability is a use-after-free [CWE-416] in the probe routine of the OMAP2430 USB MUSB controller driver. During device initialization, omap2430_probe() obtains a reference to a device tree node pointer np via the Open Firmware (OF) helpers. The driver then calls of_node_put(np) to release the reference before completing all reads from the node.
If the released reference is the last one held, the kernel frees the underlying device_node structure. Any subsequent dereference of np in either the success path or the error path reads or writes memory that has already been returned to the allocator. This creates a classic use-after-free condition inside a privileged kernel context.
The upstream fix, distributed across commits 27e62532, 632fd888, 69f9f2b3, b987f380, d53e4c41, and e194ce04, relocates the of_node_put() calls so that they execute only after the final use of np in both control-flow paths.
Root Cause
The root cause is improper lifetime management of a reference-counted device tree object. Releasing the reference before the final read violates the ownership contract of the OF API and enables the freed-object dereference.
Attack Vector
Exploitation requires local access and the ability to trigger the omap2430_probe() code path, typically through USB device binding or module loading on OMAP2430 hardware. Successful exploitation could corrupt kernel memory, leak sensitive kernel data, or crash the host. See the referenced Kernel Git Commit 27e6253 for the corrective patch details.
Detection Methods for CVE-2026-63906
Indicators of Compromise
- Unexpected kernel oops or panic messages referencing omap2430_probe in dmesg or /var/log/kern.log
- KASAN reports flagging use-after-free in the drivers/usb/musb/omap2430.c code path
- Repeated USB subsystem probe failures on OMAP2430-based systems
Detection Strategies
- Enable KASAN (Kernel Address Sanitizer) on test builds to surface use-after-free access on the np device tree node
- Audit installed kernel package versions against the fixed stable branches referenced in the patch commits
- Correlate kernel crash telemetry with USB device attach or module load events on affected hardware
Monitoring Recommendations
- Ingest kernel logs into a centralized logging pipeline and alert on BUG:, KASAN, or Oops entries mentioning omap2430
- Track kernel module load events (usbcore, musb_hdrc, omap2430) on OMAP2430 endpoints
- Monitor unprivileged process activity that precedes kernel faults for signs of local exploitation attempts
How to Mitigate CVE-2026-63906
Immediate Actions Required
- Apply the upstream Linux kernel patches referenced in the CVE and rebuild affected kernels
- Inventory OMAP2430-based devices and prioritize patching where USB MUSB is enabled in the kernel configuration
- Restrict local access to affected systems until patches are deployed
Patch Information
The vulnerability is resolved by moving the of_node_put() calls after the final use of np in both the success and error paths of omap2430_probe(). Fix commits are available at Kernel Git Commit 27e6253, Kernel Git Commit 632fd88, Kernel Git Commit 69f9f2b, Kernel Git Commit b987f38, Kernel Git Commit d53e4c4, and Kernel Git Commit e194ce0.
Workarounds
- Disable the CONFIG_USB_MUSB_OMAP2PLUS kernel option and rebuild the kernel where USB MUSB support on OMAP2430 is not required
- Prevent loading of the affected driver module via a modprobe blacklist entry until patches are applied
- Limit local shell and USB device attach privileges on OMAP2430 hardware
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
