CVE-2026-31724: 
Linux Kernel vulnerability analysis and mitigation

CVE-2026-31724 is a denial-of-service vulnerability in the Linux kernel's USB gadget f_eem driver caused by improper management of the net_device lifecycle during bind/unbind cycles. When the USB gadget function unbinds, the parent gadget device is destroyed while the net_device survives, leaving dangling sysfs symlinks that point to non-existent device tree entries. Affected kernel versions span from 3.11.1 up to (but not including) 6.12.81, 6.13 through 6.18.22, 6.19 through 6.19.12, and 7.0-rc1 through 7.0-rc6. It was published on May 1, 2026, and carries a CVSS v3.1 base score of 5.5 (Medium) (Red Hat Advisory, Red Hat Bugzilla).

The root cause is classified as CWE-459 (Incomplete Cleanup): the net_device is allocated during function instance creation and registered with the gadget device as its sysfs parent, but when the gadget function unbinds, the parent device is destroyed without properly reparenting the net_device, leaving stale sysfs symlinks (e.g., /sys/class/net/usb0 pointing to a non-existent path). The fix uses device_move() to reparent the net_device between the gadget device tree and /sys/devices/virtual across bind/unbind cycles; on final unbind, device_move(NULL) moves the device to the virtual tree before the gadget is destroyed, and on rebind it is reparented back. Exploitation requires local access with low privileges and the ability to trigger USB gadget bind/unbind operations (Red Hat Bugzilla, Red Hat Advisory).

Successful exploitation results in dangling sysfs symlinks that corrupt the device sysfs topology, potentially preventing proper device management, disrupting power management ordering, and degrading overall system stability. The impact is limited to availability (denial of service); there is no confidentiality or integrity impact. The vulnerability affects only the local system where the USB gadget driver is in use, with no known potential for lateral movement or data exposure (Red Hat Advisory, Red Hat Bugzilla).

There is no public proof-of-concept exploit and no evidence of in-the-wild exploitation as of the time of publication. The EPSS score is approximately 0.018% (0.000180), indicating a very low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog. Exploitation requires local access with low privileges and the ability to manipulate USB gadget bind/unbind cycles (Red Hat Advisory).

Update the Linux kernel to a patched version: 6.12.81 or later (for the 3.11.1–6.12.x branch), 6.18.22 or later (for the 6.13–6.18.x branch), 6.19.12 or later (for the 6.19.x branch), or kernel 7.0 stable release. Upstream patches are available via the kernel stable tree at git.kernel.org (commits a6b8bce, 4ccdccff, 14730506, d9270c9a). As a workaround, avoiding repeated USB gadget bind/unbind cycles on affected systems can reduce exposure until a patch is applied (Red Hat Advisory, Red Hat Bugzilla).