CVE-2026-98333 in Linux
Summary
by MITRE • 10/06/2026
In the Linux kernel, the following vulnerability has been resolved:
wifi: mac80211: reset the LED state when ifup fails
When the first interface comes up, the radio LED is turned on. This can start the TPT trigger timer, which continues running.
But if bringing up the interface fails then the timer keeps running and won't be stopped by anything, eventually it can be freed:
ODEBUG: free active (active state 0) object: ffff888127e12130 object type: timer_list hint: tpt_trig_timer+0x0/0x300 net/mac80211/led.c:145 WARNING: CPU: 0 PID: 5923 at lib/debugobjects.c:612 debug_print_object+0x1a2/0x2b0 debug_check_no_obj_freed+0x4b7/0x600 lib/debugobjects.c:1129 kfree+0x436/0x670 mm/slub.c:6818 ieee80211_led_exit+0x162/0x1c0 net/mac80211/led.c:210 ieee80211_unregister_hw+0x27e/0x3a0 net/mac80211/main.c:1706 rt2x00lib_remove_dev+0x55b/0x670
Undo the LED state in the error path.
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Analysis
by VulDB Data Team • 10/06/2026
The vulnerability described involves a resource management flaw within the Linux kernel's mac80211 wireless subsystem, specifically concerning the handling of hardware interface initialization failures and associated timer lifecycle management. When a network interface is brought up using the IEEE 802.11 stack, the system often activates radio LED indicators to provide visual feedback on link status or traffic activity. This activation process may initiate a throughput-based trigger timer, known as tpt_trig_timer, which monitors data transfer rates and controls LED blinking patterns based on network load. Under normal operational conditions where the interface initialization succeeds, this timer is properly managed and cleaned up when the device is eventually removed or disabled. However, if the initial bring-up sequence encounters an error during configuration or hardware registration, the kernel fails to revert the LED state and crucially does not stop the running trigger timer before proceeding with cleanup routines.
This oversight leads directly to a use-after-free condition involving kernel timers, which falls under CWE-416: Use After Free. The technical flaw arises because the error handling path in the interface setup code neglects to call the necessary functions to cancel and free the active timer instance associated with the LED trigger mechanism. As a result, when the hardware device is subsequently unregistered or removed due to the initialization failure, the cleanup routine attempts to free memory structures that are still referenced by an active kernel timer object. The debugobjects subsystem detects this inconsistency, flagging that an object of type timer_list was freed while it remained in an active state with a reference count indicating it should not yet be deallocated. This scenario creates a race condition where the timer callback might execute after its underlying data structures have been released, leading to memory corruption or kernel panic.
The operational impact of this vulnerability is primarily stability-related rather than security-exploitable for remote code execution in most standard configurations, although it can lead to denial-of-service conditions through system crashes. The presence of ODEBUG warnings and subsequent kernel panics disrupts network connectivity and requires a full system reboot if the crash occurs on critical infrastructure nodes. From an attacker's perspective, while this specific bug is triggered by local interface configuration actions rather than remote packet injection, it represents a reliability issue that could be leveraged in scenarios where an adversary has limited control over device state changes or can induce repeated initialization failures to exhaust system resources via kernel oopses and reboots. The vulnerability aligns with ATT&CK technique T1499: Endpoint Denial of Service, as the instability caused by such memory errors degrades the availability of the endpoint's networking capabilities.
Mitigation for this issue requires applying the upstream Linux kernel patch that corrects the error path in the mac80211 LED handling code. The fix ensures that if bringing up an interface fails, the system explicitly undoes any changes made to the LED state and stops the tpt_trig_timer before proceeding with hardware unregistration. Administrators should ensure their systems are updated to a kernel version containing this specific commit in net/mac80211/led.c. Additionally, enabling debugobjects warnings during development or testing phases can help identify similar resource management oversights early in the software lifecycle. For production environments, maintaining strict patching schedules and monitoring for kernel log entries related to ODEBUG violations are essential practices to detect and address such memory safety issues before they result in service disruptions.