CVE-2023-52889: Vulnerability in Linux Linux

Severity: highType: vulnerabilityCVE-2023-52889

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 <8b> 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: <IRQ> ? __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 </IRQ> <TASK> 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 <55> 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

AI Analysis

Technical Summary

CVE-2023-52889 is a vulnerability identified in the Linux kernel related to the AppArmor security module's handling of socket creation and packet processing. Specifically, the flaw arises during the creation of ICMP raw sockets when receiving ICMP packets with a security mark (secmark) set. The vulnerability is a null pointer dereference caused by a race condition where the AppArmor label context (SK_CTX(sk)->label) is updated after the packet has already been delivered to the socket. This results in the kernel attempting to access a null pointer, leading to a kernel panic and system crash. The root cause is that the packet is processed before the security label context is fully established, and the fix involves dropping packets if the label context is not set to prevent the null pointer dereference. The vulnerability manifests as a kernel oops with a detailed stack trace indicating failure in apparmor_socket_post_create and related functions. This issue affects Linux kernel versions prior to the patch and impacts systems using AppArmor with ICMP raw sockets, which are common in network diagnostic and monitoring tools. The vulnerability does not require user interaction but does require the ability to send specially crafted ICMP packets with secmark set to a vulnerable system. No known exploits are reported in the wild as of the publication date, and no CVSS score has been assigned yet.

Potential Impact

For European organizations, this vulnerability poses a risk primarily to Linux-based systems that utilize AppArmor for mandatory access control and handle ICMP raw sockets, such as servers, network appliances, and virtualized environments. Exploitation can cause kernel panics leading to denial of service (DoS), disrupting critical services and potentially causing downtime in infrastructure reliant on Linux. This is particularly impactful for sectors with high availability requirements such as finance, healthcare, telecommunications, and government agencies. The vulnerability could be leveraged by attackers to cause system crashes remotely by sending malicious ICMP packets, potentially as part of a broader attack to degrade network infrastructure or evade detection by causing instability. While it does not directly lead to privilege escalation or data breach, the availability impact and potential for service disruption are significant. Given the widespread use of Linux in European data centers and cloud environments, the vulnerability could affect a broad range of organizations if unpatched. The lack of known exploits currently reduces immediate risk but does not eliminate the threat, especially as attackers often develop exploits following public disclosure.

Mitigation Recommendations

European organizations should prioritize updating their Linux kernels to the latest patched versions that address CVE-2023-52889. Specifically, ensure that all systems running AppArmor and handling ICMP raw sockets are upgraded promptly. Network administrators should implement ingress filtering and rate limiting on ICMP traffic to reduce the risk of malicious packets reaching vulnerable hosts. Monitoring network traffic for unusual ICMP packets with secmark set can help detect potential exploitation attempts. Additionally, organizations should audit their use of AppArmor profiles and socket configurations to minimize exposure. In virtualized environments, ensure hypervisor and guest OS kernels are updated, as the vulnerability was demonstrated on VMware platforms. Employing kernel crash dump analysis tools can help identify if the vulnerability has been triggered. Finally, incorporate this vulnerability into incident response plans and vulnerability management workflows to ensure timely detection and remediation.