CVE-2023-53995 in Linux
Summary
by MITRE • 12/24/2025
In the Linux kernel, the following vulnerability has been resolved:
net: ipv4: fix one memleak in __inet_del_ifa()
I got the below warning when do fuzzing test: unregister_netdevice: waiting for bond0 to become free. Usage count = 2
It can be repoduced via:
ip link add bond0 type bond sysctl -w net.ipv4.conf.bond0.promote_secondaries=1 ip addr add 4.117.174.103/0 scope 0x40 dev bond0 ip addr add 192.168.100.111/255.255.255.254 scope 0 dev bond0 ip addr add 0.0.0.4/0 scope 0x40 secondary dev bond0 ip addr del 4.117.174.103/0 scope 0x40 dev bond0 ip link delete bond0 type bond
In this reproduction test case, an incorrect 'last_prim' is found in __inet_del_ifa(), as a result, the secondary address(0.0.0.4/0 scope 0x40) is lost. The memory of the secondary address is leaked and the reference of in_device and net_device is leaked.
Fix this problem: Look for 'last_prim' starting at location of the deleted IP and inserting the promoted IP into the location of 'last_prim'.
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Analysis
by VulDB Data Team • 02/25/2026
The vulnerability CVE-2023-53995 represents a memory leak in the Linux kernel's IPv4 networking stack, specifically within the __inet_del_ifa() function responsible for managing interface addresses. This issue manifests as a memory leak when processing secondary IP addresses on bonded network interfaces, where the kernel fails to properly track and release memory resources associated with promoted secondary addresses. The flaw occurs during the cleanup process when interface addresses are removed, creating a scenario where memory allocated for secondary addresses remains unreleased while reference counts for network device structures become inconsistent. The vulnerability is particularly concerning as it can lead to resource exhaustion over time, potentially impacting system stability and performance, especially in environments with frequent network interface modifications.
The technical root cause of this memory leak stems from improper handling of the 'last_prim' pointer within the __inet_del_ifa() function during address deletion operations. When processing secondary IP addresses that have been promoted from their original state, the kernel incorrectly identifies the location where the promoted address should be inserted, leading to a misalignment in the address list structure. This misalignment causes the secondary address information to be effectively lost from the system's tracking mechanisms, resulting in the memory allocation for that address not being properly freed. The reference counting for both the in_device and net_device structures becomes inconsistent, creating a scenario where the system maintains references to freed memory while the actual address data remains inaccessible. This issue is classified under CWE-401 as a failure to release memory resources, and specifically relates to improper memory management patterns in kernel space operations.
The operational impact of this vulnerability extends beyond simple memory consumption, creating potential security implications through resource exhaustion attacks and system instability. When repeatedly executing the described sequence of commands involving bond interface creation, address assignment, and deletion, the memory leak accumulates over time, potentially leading to system performance degradation or even system crashes under heavy network load conditions. The warning message "unregister_netdevice: waiting for bond0 to become free. Usage count = 2" indicates that the kernel is unable to properly clean up network device references, which can compound the memory leak issue and create cascading problems in network management operations. This vulnerability affects network interface management operations and can be exploited through repeated network interface modifications, making it particularly relevant for systems that frequently reconfigure network interfaces or operate in dynamic network environments.
The fix for CVE-2023-53995 addresses the core issue by modifying the address insertion logic within __inet_del_ifa() to properly locate the 'last_prim' position starting from the location of the deleted IP address rather than using incorrect positioning logic. This corrected approach ensures that promoted secondary addresses are properly reinserted into the correct position within the address list structure, preventing the loss of address information and subsequent memory leaks. The mitigation strategy involves implementing proper pointer management and ensuring that all address list manipulations maintain consistent reference counts for both in_device and net_device structures. This fix aligns with ATT&CK technique T1059.005 for system command execution and T1566.001 for malicious file execution, as it addresses a kernel-level vulnerability that could be exploited through network interface manipulation. Organizations should prioritize applying this kernel patch to prevent memory leaks and maintain system stability, particularly in environments with dynamic network configurations or high-frequency network interface modifications.