CVE-2026-64066 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
netfs: Fix netfs_read_to_pagecache() to pause on subreq failure
Fix netfs_read_to_pagecache() so that it pauses the generation of new subrequests if an already-issued subrequest fails.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability in question affects the Linux kernel's network filesystem subsystem, specifically within the netfs_read_to_pagecache() function that handles reading data into the page cache for network-based file systems. This flaw represents a critical issue in how the kernel manages asynchronous subrequests during network file operations, where the system fails to properly handle failure conditions in the request pipeline. The vulnerability manifests when the kernel attempts to read data from network storage and encounters an error with an already issued subrequest, yet continues to generate new subrequests without proper coordination or pause mechanisms.
The technical implementation flaw lies in the lack of proper error handling and state management within the netfs subsystem's request generation logic. When a subrequest fails during a network file read operation, the function should halt the creation of additional subrequests until the failure is properly addressed or the overall operation can be safely resumed. However, the flawed implementation continues to spawn new subrequests even after detecting failures in previous ones, leading to potential resource exhaustion, inconsistent data states, and system instability. This behavior creates a cascade effect where multiple failed subrequests generate further unnecessary load on both the network infrastructure and kernel memory management subsystems.
The operational impact of this vulnerability extends beyond simple performance degradation to potentially enabling denial of service conditions within network filesystem environments. When the kernel continues issuing new subrequests despite encountering failures, it can overwhelm network resources and cause memory allocation issues that may result in system crashes or unresponsive file operations. Network filesystems such as nfs, cifs, and other distributed storage protocols that rely on this subsystem are particularly vulnerable, as they frequently use asynchronous read operations to optimize data transfer patterns. The vulnerability essentially allows an attacker to potentially trigger resource exhaustion through carefully crafted network read operations, leading to system instability or complete service disruption.
Mitigation strategies for this vulnerability involve ensuring proper error propagation and request coordination within the netfs subsystem. System administrators should prioritize applying kernel updates that contain the specific fix for netfs_read_to_pagecache() function behavior, which implements the required pause mechanism when subrequest failures occur. The fix aligns with established security practices by implementing proper state management and error handling protocols that prevent cascading failures in asynchronous operations. Organizations should also monitor network filesystem usage patterns and implement appropriate resource limits or timeouts to minimize potential impact if the vulnerability exists in older kernel versions. This approach addresses the underlying CWE-691 weakness related to insufficient control flow management and aligns with ATT&CK techniques targeting system stability through resource exhaustion attacks. The fix demonstrates proper defensive programming practices by ensuring that failure conditions trigger appropriate state transitions and prevent further problematic operations until recovery can be safely achieved.