CVE-2026-80885 in Linux
Summary
by MITRE • 09/04/2026
In the Linux kernel, the following vulnerability has been resolved:
afs: Fix uncancelled rxrpc OOB message handler
Fix AFS to cancel its OOB message processing (typically to respond to security challenges). Also move OOB message processing to afs_wq so that it's also waited for and make the OOB handler just return if the net namespace is no longer live.
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Analysis
by VulDB Data Team • 09/04/2026
The Advanced File System, commonly known as AFS, relies on the rxrpc protocol implementation within the Linux kernel to manage network communications with remote servers. This vulnerability addresses a critical flaw in how out-of-band messages are handled during the lifecycle of an AFS connection. Out-of-band messages typically carry urgent control information, such as security challenges required for authentication or session management. The core issue stemmed from improper cancellation mechanisms when these message handlers were invoked but no longer needed due to connection teardown or namespace unloading. Without proper cleanup, resources associated with pending out-of-band processing could remain allocated indefinitely or be accessed after the underlying network context had been destroyed.
The technical flaw involved a race condition and resource leak where the rxrpc out-of-band message handler did not correctly cancel its operations when the AFS connection was being terminated. This lack of cancellation meant that if an out-of-band message arrived while the system was attempting to close or reset the connection, the processing logic might continue executing even after the relevant data structures were freed. Furthermore, the original implementation allowed this processing to occur in a context where it was not properly synchronized with the net namespace lifecycle. If the network namespace associated with the AFS volume was destroyed while an out-of-band handler was still active or queued for execution, subsequent access to namespace-specific resources would result in use-after-free conditions or null pointer dereferences, potentially leading to kernel panics or arbitrary code execution depending on memory layout and exploitation techniques.
To resolve this issue, the fix implements a robust cancellation mechanism that ensures all pending out-of-band message processing is explicitly aborted when an AFS connection is closed. This prevents orphaned tasks from continuing to operate in stale contexts. Additionally, the patch moves the handling of these messages to afs_wq, which is a dedicated workqueue for AFS operations. By utilizing this specific workqueue, the kernel ensures that all out-of-band processing tasks are properly waited upon and synchronized during shutdown sequences. This architectural change guarantees that no asynchronous task remains active after the net namespace has been marked as dead. The handler itself was also updated to check if the network namespace is still live before proceeding with any operations, providing an additional layer of safety against accessing invalid memory regions associated with destroyed namespaces.
The operational impact of this vulnerability includes potential denial-of-service through kernel crashes and possible privilege escalation via use-after-free exploits. An attacker who can trigger AFS connections and manipulate timing to cause out-of-band message processing during teardown could exploit these race conditions. The fix significantly improves the stability and security posture of the Linux kernel by eliminating a class of memory safety errors related to asynchronous network I/O cleanup. This aligns with industry standards for secure coding practices, specifically addressing CWE-416 Use After Free and CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization Race Condition. From an ATT&CK perspective, this mitigates techniques associated with exploitation of binary vulnerabilities in kernel components to gain higher privileges or disrupt service availability. System administrators should ensure that the Linux kernel is updated to a version containing these patches to prevent potential exploitation against AFS-enabled systems.