CVE-2026-64069 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
netfs: Fix cancellation of a DIO and single read subrequests
When the preparation of a new subrequest for a read fails, if the subrequest has already been added to the stream->subrequests list, it can't simply be put and abandoned as the collector may see it. Also, if it hasn't been queued yet, it has two outstanding refs that both need to be put. Both DIO read and single-read dispatch fail at this; further, both differ in the order they do things to the way buffered read works.
Fix cancellation of both DIO-read and single-read subrequests that failed preparation by the following steps:
(1) Harmonise all three reads (buffered, dio, single) to queue the subreq before prepping it.
(2) Make all three call netfs_queue_read() to do the queuing.
(3) Set NETFS_RREQ_ALL_QUEUED independently of the queuing as we don't know the length of the subreq at this point.
(4) In all cases, set the error and NETFS_SREQ_FAILED flag on the subreq and then call netfs_read_subreq_terminated() to deal with it. This will pass responsibility off to the collector for dealing with it.
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Analysis
by VulDB Data Team • 07/20/2026
This vulnerability resides in the Linux kernel's network filesystem subsystem, specifically addressing a critical flaw in how subrequests are handled during read operations. The issue manifests when preparing new subrequests for read operations fails, creating a scenario where memory management and request state synchronization become compromised. The vulnerability affects both direct I/O (DIO) reads and single-read dispatch mechanisms, which are fundamental components of the kernel's file system handling architecture.
The technical flaw stems from improper handling of subrequest lifecycle management within the netfs subsystem. When subrequest preparation fails, the code path does not correctly account for requests that have already been added to the stream->subrequests list, potentially leading to race conditions where the request collector processes partially initialized requests. Additionally, requests that haven't yet been queued face a dual reference counting issue where two outstanding references must be properly released, creating potential memory leaks or use-after-free scenarios. This problem is particularly dangerous because it affects core read operations that are frequently executed throughout system operation.
The operational impact of this vulnerability extends across multiple attack vectors within the Linux kernel's network file system processing. Attackers could potentially exploit this weakness to cause system instability through resource exhaustion, leading to denial of service conditions or even privilege escalation scenarios. The vulnerability affects systems using network filesystems such as NFS, CIFS, and other network-based storage solutions that rely on the netfs subsystem for read request handling. Given that these are fundamental kernel operations, the impact spans across various deployment scenarios from desktop systems to enterprise servers.
The fix implements a harmonized approach to subrequest management across all three read types: buffered, DIO, and single-read operations. This solution restructures the preparation sequence by ensuring all three read mechanisms queue subrequests before attempting preparation, thereby establishing consistent state management. The implementation leverages the netfs_queue_read() function uniformly across all code paths, creating a standardized queuing mechanism that eliminates the race conditions inherent in the previous approach. The fix also introduces proper error flag setting with NETFS_RREQ_ALL_QUEUED being set independently of queuing operations, ensuring correct request state tracking.
The mitigation strategy follows established security principles by centralizing error handling through netfs_read_subreq_terminated() function calls, which properly delegates responsibility to the collector component for final cleanup. This approach aligns with CWE-457: Use of Uninitialized Variable and addresses potential memory safety issues classified under ATT&CK technique T1059.008 for kernel-level privilege escalation risks. The solution ensures proper reference counting through consistent flag setting including NETFS_SREQ_FAILED, which prevents dangling references and maintains system stability during concurrent read operations. This comprehensive fix not only resolves the immediate vulnerability but also establishes a more robust framework for future subrequest handling within the Linux kernel's network filesystem subsystem.
The implementation demonstrates adherence to secure coding practices by addressing state management inconsistencies across different read operation types. The harmonization of queuing order and error propagation mechanisms creates a predictable execution flow that eliminates the conditions leading to resource leaks or system instability. This vulnerability resolution represents a significant improvement in kernel security posture, particularly for systems relying heavily on network filesystem operations where such race conditions could be exploited for persistent system compromise.