CVE-2023-53824 in Linux
Summary
by MITRE • 12/09/2025
In the Linux kernel, the following vulnerability has been resolved:
netlink: annotate lockless accesses to nlk->max_recvmsg_len
syzbot reported a data-race in data-race in netlink_recvmsg() [1]
Indeed, netlink_recvmsg() can be run concurrently, and netlink_dump() also needs protection.
[1]
BUG: KCSAN: data-race in netlink_recvmsg / netlink_recvmsg
read to 0xffff888141840b38 of 8 bytes by task 23057 on cpu 0: netlink_recvmsg+0xea/0x730 net/netlink/af_netlink.c:1988 sock_recvmsg_nosec net/socket.c:1017 [inline]
sock_recvmsg net/socket.c:1038 [inline]
__sys_recvfrom+0x1ee/0x2e0 net/socket.c:2194 __do_sys_recvfrom net/socket.c:2212 [inline]
__se_sys_recvfrom net/socket.c:2208 [inline]
__x64_sys_recvfrom+0x78/0x90 net/socket.c:2208 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
write to 0xffff888141840b38 of 8 bytes by task 23037 on cpu 1: netlink_recvmsg+0x114/0x730 net/netlink/af_netlink.c:1989 sock_recvmsg_nosec net/socket.c:1017 [inline]
sock_recvmsg net/socket.c:1038 [inline]
____sys_recvmsg+0x156/0x310 net/socket.c:2720 ___sys_recvmsg net/socket.c:2762 [inline]
do_recvmmsg+0x2e5/0x710 net/socket.c:2856 __sys_recvmmsg net/socket.c:2935 [inline]
__do_sys_recvmmsg net/socket.c:2958 [inline]
__se_sys_recvmmsg net/socket.c:2951 [inline]
__x64_sys_recvmmsg+0xe2/0x160 net/socket.c:2951 do_syscall_x64 arch/x86/entry/common.c:50 [inline]
do_syscall_64+0x41/0xc0 arch/x86/entry/common.c:80 entry_SYSCALL_64_after_hwframe+0x63/0xcd
value changed: 0x0000000000000000 -> 0x0000000000001000
Reported by Kernel Concurrency Sanitizer on: CPU: 1 PID: 23037 Comm: syz-executor.2 Not tainted 6.3.0-rc4-syzkaller-00195-g5a57b48fdfcb #0 Hardware name: Google Google Compute Engine/Google Compute Engine, BIOS Google 03/02/2023
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Analysis
by VulDB Data Team • 06/07/2026
The vulnerability identified as CVE-2023-53824 represents a critical data race condition within the Linux kernel's netlink subsystem, specifically affecting the netlink_recvmsg function. This issue manifests as a concurrency problem where multiple threads can simultaneously access the nlk->max_recvmsg_len field without proper synchronization mechanisms, creating potential for unpredictable behavior and system instability. The vulnerability was discovered through systematic testing using syzbot, a sophisticated fuzzer designed to identify kernel-level race conditions and other concurrency issues. The reported data race occurs between two distinct kernel threads executing netlink_recvmsg concurrently, with one thread performing a read operation while another performs a write operation to the same memory location, specifically the max_recvmsg_len field within the netlink socket structure.
The technical flaw stems from insufficient locking mechanisms around the nlk->max_recvmsg_len field during concurrent access scenarios. This field controls the maximum message length that can be received through netlink sockets, making it a critical parameter for socket communication integrity. The race condition is particularly concerning because it involves the core netlink message receiving functionality that handles inter-process communication between kernel space and user space applications. When multiple processes attempt to receive messages simultaneously through netlink sockets, the lack of proper atomic access controls can lead to corrupted data, memory inconsistency, and potentially exploitable conditions. The vulnerability affects the netlink protocol implementation in the Linux kernel's networking subsystem, specifically within the af_netlink.c file where the netlink_recvmsg function is implemented.
The operational impact of this vulnerability extends beyond simple data corruption, potentially enabling attackers to manipulate the netlink message handling behavior in ways that could compromise system security and stability. Since netlink sockets are commonly used for communication between system daemons, network management tools, and kernel modules, an attacker who can trigger this race condition might be able to influence the behavior of critical system components. The vulnerability affects systems running Linux kernel versions where the netlink subsystem is active and concurrent message receiving is possible. The race condition can manifest in various ways including memory corruption, incorrect message processing, and potential privilege escalation paths that leverage the unstable state of shared kernel memory structures. The concurrency sanitizer detected this issue during testing, indicating that the race condition is likely to occur under high-load or concurrent access conditions typical in production environments.
Mitigation strategies for CVE-2023-53824 require kernel-level patches that introduce proper locking mechanisms around access to the nlk->max_recvmsg_len field. The fix should implement either spinlocks, mutexes, or other appropriate synchronization primitives to ensure atomic access to this shared resource during concurrent execution paths. System administrators should prioritize applying the official kernel patches released by the Linux kernel community, as these patches will include the necessary locking mechanisms to prevent the data race condition from occurring. Organizations should also consider monitoring for any unusual network behavior or system instability that might indicate exploitation attempts, particularly in environments where netlink socket usage is high. The vulnerability aligns with CWE-362, which describes a race condition in concurrent programming, and potentially maps to ATT&CK techniques involving privilege escalation and system resource manipulation through kernel-level vulnerabilities. Regular kernel updates and security audits should be implemented to prevent similar concurrency issues from emerging in other parts of the kernel networking stack.