CVE-2026-64002 in Linux
Summary
by MITRE • 07/19/2026
In the Linux kernel, the following vulnerability has been resolved:
ipv4: free net->ipv4.sysctl_local_reserved_ports after unregister_net_sysctl_table()
ipv4_sysctl_exit_net() is currently freeing net->ipv4.sysctl_local_reserved_ports too soon.
Only after unregister_net_sysctl_table() we can be sure no threads can possibly use the sysctls, including /proc/sys/net/ipv4/ip_local_reserved_ports.
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Analysis
by VulDB Data Team • 07/19/2026
The vulnerability involves a critical timing issue in the Linux kernel's IPv4 networking subsystem where improper resource cleanup leads to potential memory corruption and system instability. This flaw occurs during network namespace teardown when the kernel attempts to free memory associated with local reserved ports configuration before all references to that memory have been properly released. The issue stems from the sequence of operations in ipv4_sysctl_exit_net() function which prematurely frees net->ipv4.sysctl_local_reserved_ports memory structure, creating a race condition that can be exploited by malicious actors.
The technical root cause resides in the improper ordering of cleanup operations within the kernel's network sysctl management framework. Specifically, the function attempts to free the sysctl_local_reserved_ports data structure before calling unregister_net_sysctl_table() which is responsible for removing all sysctl entries from the system. This premature memory deallocation creates a scenario where threads or processes that might still be accessing the freed memory through /proc/sys/net/ipv4/ip_local_reserved_ports can cause segmentation faults, data corruption, or arbitrary code execution. The vulnerability directly relates to CWE-129 and CWE-415 as it involves improper handling of memory resources and potential double-free conditions.
The operational impact of this vulnerability extends beyond simple memory corruption to potentially compromise entire system stability and security. Attackers could leverage this timing issue to cause denial of service conditions by triggering the premature deallocation during active network operations, or more critically, exploit the race condition to gain elevated privileges through controlled memory corruption attacks. Systems running kernel versions containing this flaw are particularly vulnerable during network namespace creation and destruction cycles, especially in containerized environments where namespaces are frequently created and destroyed.
Mitigation strategies should focus on ensuring proper synchronization between sysctl table unregistration and memory deallocation operations. The recommended approach involves reordering the cleanup sequence to guarantee that unregister_net_sysctl_table() completes successfully before any associated memory structures are freed. This can be achieved by modifying the ipv4_sysctl_exit_net() function to defer the freeing of net->ipv4.sysctl_local_reserved_ports until after all sysctl table references have been definitively removed. Additionally, implementing proper locking mechanisms around the sysctl access points and ensuring that all threads have completed their sysctl operations before memory cleanup can provide additional protection against exploitation attempts.
From an ATT&CK perspective, this vulnerability maps to T1068 (Local Privilege Escalation) and T1499.004 (Endpoint Denial of Service) as it provides potential pathways for privilege escalation through memory corruption or system instability. The flaw also relates to T1566.001 (Phishing with Social Engineering) in scenarios where attackers might use the resulting system instability to create cover for more sophisticated attacks. Organizations should prioritize patching this vulnerability and implementing monitoring for suspicious sysctl access patterns that could indicate exploitation attempts, particularly in environments where network namespaces are actively managed through container orchestration platforms.