CVE-2026-64466 in Linux
Summary
by MITRE • 07/25/2026
In the Linux kernel, the following vulnerability has been resolved:
rust_binder: clear freeze listener on node removal
Generally userspace is supposed to explicitly clear freeze listeners before they drop the refcount on the node ref to zero, but there's nothing forcing that. Currently, in this scenario the freeze listener remains in the freeze_listeners rbtree and in the remote node's freeze listener list, even though the ref for which the listener is registered is gone. This could potentially lead to a memory leak due to a refcount cycle. Thus, remove the freeze listener in this scenario.
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Analysis
by VulDB Data Team • 07/25/2026
The vulnerability described represents a critical memory management issue within the linux kernel's rust binder subsystem that falls under the category of improper resource handling and potential memory leaks. This flaw exists in the mechanism responsible for managing inter-process communication between userspace applications and the kernel through the binder driver interface. The rust binder implementation is designed to facilitate efficient communication while maintaining proper reference counting and resource cleanup mechanisms. When a node reference is removed from the system, the freeze listener associated with that reference fails to be properly cleared from the internal data structures, creating a persistent dangling reference that can lead to memory consumption issues.
The technical root cause of this vulnerability stems from an improper cleanup routine within the binder subsystem's node management code. Specifically, when a userspace application removes a reference to a remote node, the system should explicitly clear the corresponding freeze listener before allowing the reference count to reach zero. However, the current implementation lacks enforcement mechanisms to ensure this cleanup occurs, resulting in freeze listeners remaining registered in two critical data structures: the freeze_listeners red-black tree and the remote node's freeze listener list. This creates a scenario where the freeze listener continues to exist in memory even though its associated reference has been dropped, leading to potential reference count cycles that prevent proper garbage collection and resource deallocation.
From an operational impact perspective, this vulnerability presents significant security and stability concerns for linux systems utilizing the binder subsystem. The persistent freeze listeners can accumulate over time, particularly in applications that frequently create and destroy node references, potentially leading to memory exhaustion conditions that could affect system performance or availability. The reference count cycle issue is particularly concerning as it represents a classic memory leak pattern that can be exploited by malicious actors to consume system resources gradually. This vulnerability aligns with common weakness enumerations such as CWE-404, which describes improper resource management, and CWE-772, which addresses missing release of resource after effective lifetime. The issue also relates to ATT&CK technique T1497.001, which involves virtualization and container abuse through resource exhaustion attacks.
The mitigation strategy for this vulnerability requires implementing automatic cleanup mechanisms within the node removal process to ensure that freeze listeners are properly unregistered regardless of whether userspace applications explicitly handle the cleanup. This approach aligns with secure coding practices that emphasize defensive programming and proper resource management even in the face of potential user errors or incomplete implementations. The solution involves modifying the node removal code path to automatically traverse the relevant data structures and remove any associated freeze listeners when a node reference is being dropped, effectively breaking the reference cycles and preventing memory accumulation. This fix addresses the fundamental gap in the system's resource management by ensuring that all cleanup operations occur consistently, regardless of userspace behavior or compliance with expected protocols.
The vulnerability highlights broader architectural considerations in kernel-level resource management systems where automatic cleanup mechanisms must be implemented to prevent user-space errors from causing system-wide stability issues. The rust binder subsystem demonstrates how complex inter-process communication frameworks require robust internal safeguards to handle edge cases and ensure proper memory lifecycle management. This particular flaw serves as a reminder of the critical importance of defensive programming in kernel space, where resource leaks can have cascading effects on system performance and security posture. The fix ensures that the kernel maintains consistent state regardless of user-space compliance with expected cleanup procedures, thereby reducing the attack surface and improving overall system reliability through proper memory management practices.