CVE-2026-72126 in Linux
Summary
by MITRE • 08/15/2026
In the Linux kernel, the following vulnerability has been resolved:
can: isotp: use unconditional synchronize_rcu() in isotp_release()
isotp_notify() unregisters the (RCU) CAN filters via can_rx_unregister() and clears so->bound without waiting for a grace period. isotp_release() uses so->bound to decide whether it needs to call synchronize_rcu() before cancelling so->rxtimer, so when NETDEV_UNREGISTER runs first it skips that synchronize_rcu() and can cancel the timer while an in-flight isotp_rcv() is still executing and about to re-arm it via isotp_send_fc(), leading to a use-after-free timer callback on the freed socket.
sakisho-bot remarked a problem with rtnl_lock held in isotp_notify(), therefore make isotp_release() always call synchronize_rcu() before cancelling the timers, regardless of so->bound. This still closes the original race (isotp_notify() clearing so->bound without waiting for in-flight isotp_rcv() callers before isotp_release() cancels the RX timer) without adding any RCU wait to the netdevice notifier path.
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Analysis
by VulDB Data Team • 08/15/2026
The vulnerability resides within the Linux kernel's CAN (Controller Area Network) protocol implementation, specifically in the ISO Transport Protocol (ISOTP) layer that handles communication between automotive systems and other networked devices. This issue manifests as a race condition that can lead to use-after-free conditions when network devices are unregistered while ISOTP socket operations are in progress. The problem occurs during the cleanup phase of ISOTP socket release operations, where improper synchronization mechanisms leave room for memory corruption vulnerabilities.
The technical flaw stems from the improper handling of RCU (Read-Copy-Update) synchronization within the isotp_release() function. When a network device is unregistered, the isotp_notify() function executes and unregisters CAN filters through can_rx_unregister() while clearing the so->bound flag without waiting for a grace period. This premature clearing causes isotp_release() to make incorrect decisions about whether to invoke synchronize_rcu() before canceling the RX timer. The race condition creates a scenario where the timer cancellation occurs while in-flight isotp_rcv() functions might still be executing, potentially leading to memory corruption when these functions attempt to re-arm the timer via isotp_send_fc() after the socket has been freed.
This vulnerability directly relates to CWE-362, which describes concurrent execution issues such as race conditions that can lead to improper handling of resources. The flaw also maps to ATT&CK technique T1059.007 for Windows and related techniques for kernel-level privilege escalation through memory corruption. The issue demonstrates how improper synchronization in kernel space can provide attackers with opportunities to execute arbitrary code or cause system instability, particularly in automotive environments where CAN networks are critical for vehicle operation.
The operational impact of this vulnerability is significant in automotive and industrial control systems that rely on Linux-based CAN networking. When network devices are unregistered during active ISOTP communication, the race condition could lead to system crashes, memory corruption, or potentially exploitable conditions that might allow attackers to gain elevated privileges. The vulnerability affects any system using the Linux kernel's ISOTP implementation where CAN network devices may be dynamically removed while socket operations are in progress.
The mitigation strategy involves modifying isotp_release() to always call synchronize_rcu() before canceling timers, regardless of the so->bound flag state. This unconditional approach eliminates the race condition without introducing additional RCU waits in the netdevice notifier path that could impact system performance. The solution addresses the root cause by ensuring proper synchronization regardless of the timing of device unregister operations, preventing the use-after-free scenario where timer callbacks attempt to access freed memory structures. This approach maintains system stability while preserving the performance characteristics of the original implementation.