CVE-2023-52889 in Linux
Summary
by MITRE • 08/17/2024
In the Linux kernel, the following vulnerability has been resolved:
apparmor: Fix null pointer deref when receiving skb during sock creation
The panic below is observed when receiving ICMP packets with secmark set while an ICMP raw socket is being created. SK_CTX(sk)->label is updated in apparmor_socket_post_create(), but the packet is delivered to the socket before that, causing the null pointer dereference. Drop the packet if label context is not set.
BUG: kernel NULL pointer dereference, address: 000000000000004c #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page PGD 0 P4D 0 Oops: 0000 [#1] PREEMPT SMP NOPTI
CPU: 0 PID: 407 Comm: a.out Not tainted 6.4.12-arch1-1 #1 3e6fa2753a2d75925c34ecb78e22e85a65d083df Hardware name: VMware, Inc. VMware Virtual Platform/440BX Desktop Reference Platform, BIOS 6.00 05/28/2020 RIP: 0010:aa_label_next_confined+0xb/0x40 Code: 00 00 48 89 ef e8 d5 25 0c 00 e9 66 ff ff ff 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 66 0f 1f 00 0f 1f 44 00 00 89 f0 77 4c 39 c6 7e 1f 48 63 d0 48 8d 14 d7 eb 0b 83 c0 01 48 83 c2 RSP: 0018:ffffa92940003b08 EFLAGS: 00010246 RAX: 0000000000000000 RBX: 0000000000000000 RCX: 000000000000000e RDX: ffffa92940003be8 RSI: 0000000000000000 RDI: 0000000000000000 RBP: ffff8b57471e7800 R08: ffff8b574c642400 R09: 0000000000000002 R10: ffffffffbd820eeb R11: ffffffffbeb7ff00 R12: ffff8b574c642400 R13: 0000000000000001 R14: 0000000000000001 R15: 0000000000000000 FS: 00007fb092ea7640(0000) GS:ffff8b577bc00000(0000) knlGS:0000000000000000 CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 CR2: 000000000000004c CR3: 00000001020f2005 CR4: 00000000007706f0 PKRU: 55555554 Call Trace: ? __die+0x23/0x70 ? page_fault_oops+0x171/0x4e0 ? exc_page_fault+0x7f/0x180 ? asm_exc_page_fault+0x26/0x30 ? aa_label_next_confined+0xb/0x40 apparmor_secmark_check+0xec/0x330 security_sock_rcv_skb+0x35/0x50 sk_filter_trim_cap+0x47/0x250 sock_queue_rcv_skb_reason+0x20/0x60 raw_rcv+0x13c/0x210 raw_local_deliver+0x1f3/0x250 ip_protocol_deliver_rcu+0x4f/0x2f0 ip_local_deliver_finish+0x76/0xa0 __netif_receive_skb_one_core+0x89/0xa0 netif_receive_skb+0x119/0x170 ? __netdev_alloc_skb+0x3d/0x140 vmxnet3_rq_rx_complete+0xb23/0x1010 [vmxnet3 56a84f9c97178c57a43a24ec073b45a9d6f01f3a]
vmxnet3_poll_rx_only+0x36/0xb0 [vmxnet3 56a84f9c97178c57a43a24ec073b45a9d6f01f3a]
__napi_poll+0x28/0x1b0 net_rx_action+0x2a4/0x380 __do_softirq+0xd1/0x2c8 __irq_exit_rcu+0xbb/0xf0 common_interrupt+0x86/0xa0 asm_common_interrupt+0x26/0x40 RIP: 0010:apparmor_socket_post_create+0xb/0x200 Code: 08 48 85 ff 75 a1 eb b1 0f 1f 80 00 00 00 00 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 90 f3 0f 1e fa 0f 1f 44 00 00 41 54 48 89 fd 53 45 85 c0 0f 84 b2 00 00 00 48 8b 1d 80 56 3f 02 48 RSP: 0018:ffffa92940ce7e50 EFLAGS: 00000286 RAX: ffffffffbc756440 RBX: 0000000000000000 RCX: 0000000000000001 RDX: 0000000000000003 RSI: 0000000000000002 RDI: ffff8b574eaab740 RBP: 0000000000000001 R08: 0000000000000000 R09: 0000000000000000 R10: ffff8b57444cec70 R11: 0000000000000000 R12: 0000000000000003 R13: 0000000000000002 R14: ffff8b574eaab740 R15: ffffffffbd8e4748 ? __pfx_apparmor_socket_post_create+0x10/0x10 security_socket_post_create+0x4b/0x80 __sock_create+0x176/0x1f0 __sys_socket+0x89/0x100 __x64_sys_socket+0x17/0x20 do_syscall_64+0x5d/0x90 ? do_syscall_64+0x6c/0x90 ? do_syscall_64+0x6c/0x90 ? do_syscall_64+0x6c/0x90 entry_SYSCALL_64_after_hwframe+0x72/0xdc
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Analysis
by VulDB Data Team • 02/01/2026
The vulnerability identified as CVE-2023-52889 resides within the Linux kernel's AppArmor security module, specifically addressing a null pointer dereference issue that occurs during socket creation and ICMP packet handling. This flaw manifests when an ICMP raw socket is being created while ICMP packets with secmark set are simultaneously received. The root cause lies in the timing of when the socket label context is updated versus when packets are delivered to the socket, creating a window where the security label is not yet initialized, leading to a kernel panic upon access to an uninitialized memory location.
The technical execution of this vulnerability involves the apparmor_socket_post_create() function which updates the socket's label context in SK_CTX(sk)->label. However, packets are delivered to the socket before this update occurs, resulting in a null pointer dereference when the packet processing code attempts to access the uninitialized label. The crash occurs in the aa_label_next_confined() function which is part of the AppArmor security framework's packet filtering mechanism. This function attempts to access a memory address that is set to zero due to the uninitialized label, triggering a kernel NULL pointer dereference that results in system instability and potential denial of service.
The operational impact of this vulnerability extends beyond simple system crashes, as it can be exploited to cause a denial of service condition within systems running affected kernel versions. Attackers could potentially leverage this weakness by creating ICMP raw sockets while simultaneously flooding the system with specially crafted ICMP packets that have secmark set. This scenario would lead to repeated kernel panics and system instability, particularly affecting network services that rely heavily on ICMP processing. The vulnerability affects systems using the Linux kernel version 6.4.12 and potentially earlier versions, making it a critical concern for network infrastructure and security-sensitive environments where AppArmor is deployed.
Mitigation strategies for CVE-2023-52889 focus on patching the kernel to the fixed version where the null pointer dereference is resolved. The fix implemented in the AppArmor module involves dropping packets if the label context is not yet set, preventing the access to uninitialized memory. System administrators should prioritize updating their kernel versions to include the patch that resolves this issue. Additionally, monitoring for unusual ICMP traffic patterns and implementing network-level controls to limit ICMP packet flooding can serve as temporary protective measures. The vulnerability aligns with CWE-476 which describes null pointer dereference, and can be mapped to ATT&CK technique T1499.004 which covers network disruption through denial of service attacks, highlighting the potential for exploitation in network-based attacks.
This vulnerability demonstrates the complexity of security module integration within kernel space and the importance of careful synchronization between different subsystems. The timing issue between socket creation and packet delivery highlights the need for robust synchronization primitives in kernel security frameworks. The fix implemented in the AppArmor module represents a defensive programming approach where packet validation is performed before accessing potentially uninitialized structures, preventing the kernel from crashing while maintaining system stability. Organizations should ensure their systems are updated with the latest kernel patches and consider implementing network segmentation to limit the impact of such vulnerabilities on critical network services.