CVE-2026-64068 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
netfs: Fix missing locking around retry adding new subreqs
Fix netfs_retry_read_subrequests() and netfs_retry_write_stream() to take the appropriate lock when adding extra subrequests into stream->subrequests.
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Analysis
by VulDB Data Team • 07/19/2026
This vulnerability exists within the linux kernel's network filesystem implementation where improper synchronization mechanisms lead to potential race conditions during subrequest handling. The flaw specifically affects the netfs subsystem which manages network file operations and their associated subrequests that represent individual data transfer operations within larger file operations. When the kernel attempts to retry failed read or write operations, it must add additional subrequests to existing streams to handle the retry logic. Without proper locking mechanisms in place, concurrent access to the stream->subrequests data structure can result in corrupted data structures and unpredictable behavior.
The technical implementation issue stems from two primary functions: netfs_retry_read_subrequests() and netfs_retry_write_stream() which are responsible for managing retry operations when network file operations fail. These functions need to ensure exclusive access to the stream->subrequests list when adding new subrequests during retry scenarios. The missing locking mechanism creates a window where multiple threads or processes could simultaneously modify the same subrequest list, leading to memory corruption, data inconsistency, and potential system instability. This type of race condition falls under CWE-362 which specifically addresses Race Conditions and CWE-116 which covers improper use of synchronization primitives.
The operational impact of this vulnerability can be severe in network filesystem environments where concurrent access is common. Systems utilizing nfs, cifs, or other network file systems may experience data corruption, application crashes, or system hangs when retry operations are triggered. Attackers could potentially exploit this race condition to cause denial of service conditions or in rare cases might be able to manipulate the data flow to gain unauthorized access to network resources. The vulnerability is particularly dangerous in high-concurrency environments where multiple processes simultaneously attempt file operations and retries.
Mitigation strategies should focus on implementing proper locking mechanisms around the affected functions to ensure atomic access to stream->subrequests. System administrators should apply the kernel patch that adds appropriate mutex or spinlock acquisition before modifying the subrequest lists during retry operations. Regular kernel updates and security patches should be prioritized for all network filesystem deployments, especially in enterprise environments where multiple concurrent file operations are common. Monitoring for unusual system behavior or file operation failures can help identify potential exploitation attempts. The fix aligns with ATT&CK technique T1499.001 which involves denial of service through resource exhaustion, and the vulnerability demonstrates how improper synchronization can create conditions that lead to system instability. Organizations should also consider implementing network segmentation and access controls to limit exposure of vulnerable network filesystem services.