CVE-2026-64002: ipv4: free net->ipv4.sysctl_local_reserved_ports after unregister_net_sysctl_table()
In the Linux kernel, the following vulnerability has been resolved:
ipv4: free net->ipv4.sysctllocalreservedports after unregisternetsysctltable()
ipv4sysctlexitnet() is currently freeing net->ipv4.sysctllocalreservedports too soon.
Only after unregisternetsysctltable() we can be sure no threads can possibly use the sysctls, including /proc/sys/net/ipv4/iplocalreservedports.
Other sources
In the Linux kernel, the following vulnerability has been resolved:
ipv4: free net-ipv4.sysctllocalreservedports after unregisternetsysctltable()
ipv4sysctlexitnet() is currently freeing net-ipv4.sysctllocalreservedports too soon.
Only after unregisternetsysctltable() we can be sure no threads can possibly use the sysctls, including /proc/sys/net/ipv4/iplocalreservedports.
— IBM
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Compensating control
In ipv4_sysctl_exit_net(), free net->ipv4.sysctl_local_reserved_ports only after unregister_net_sysctl_table(), including for the /proc/sys/net/ipv4/ip_local_reserved_ports sysctl.
Event History
Frequently Asked Questions
What conditions are needed to trigger this issue?
The issue involves concurrent access to the IPv4 sysctl interface, specifically /proc/sys/net/ipv4/ip_local_reserved_ports, while the associated network namespace sysctl state is being torn down. Exploitation requires local access with low privileges; no user interaction is required.
Are systems using the affected sysctl interface potentially exposed by default?
The vulnerable interface is the IPv4 sysctl path /proc/sys/net/ipv4/ip_local_reserved_ports. The provided information does not state whether a particular kernel configuration or default deployment must enable or modify this setting.
What is the practical impact of successful exploitation?
This is a use-after-free condition in the Linux kernel. The supplied severity vector indicates potential high impact to confidentiality, integrity, and availability.
How can I determine whether a fix is available for my kernel?
Check whether your kernel includes one of the referenced stable commits: 155f90be5ee8be5b110ebc0b7da33c54c83b0208, 5b23a2ff379e70b6b9ff744a972b63e1f8f4d996, or 6512c57c4638ddec113bf42439361ba85a12048d. The provided data does not identify fixed kernel release versions.