CVE-2023-51781 in Linux
Summary
by MITRE • 01/11/2024
An issue was discovered in the Linux kernel before 6.6.8. atalk_ioctl in net/appletalk/ddp.c has a use-after-free because of an atalk_recvmsg race condition.
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Analysis
by VulDB Data Team • 01/11/2024
The vulnerability identified as CVE-2023-51781 represents a critical use-after-free condition affecting the Linux kernel version prior to 6.6.8. This flaw resides within the AppleTalk protocol implementation specifically in the atalk_ioctl function located in net/appletalk/ddp.c. The issue stems from a race condition that occurs during the atalk_recvmsg operation, creating a window where memory resources become invalid while still being referenced by the system. The AppleTalk protocol, although largely deprecated in modern networking environments, remains present in kernel space and continues to pose security risks due to its complex implementation and interaction with other kernel subsystems.
The technical nature of this vulnerability manifests through a classic race condition scenario where concurrent access to shared kernel resources creates a timing window for memory management errors. When atalk_recvmsg processes incoming AppleTalk messages, the race condition allows for a situation where a memory buffer allocated for protocol handling can be freed while another kernel thread or process continues to reference it. This use-after-free scenario enables arbitrary code execution capabilities as attackers can manipulate the freed memory to redirect execution flow or corrupt kernel data structures. The vulnerability specifically affects the AppleTalk Datagram Delivery Protocol implementation which handles packet routing and delivery within the legacy AppleTalk networking framework.
The operational impact of CVE-2023-51781 extends beyond simple privilege escalation as it represents a kernel-level vulnerability that can be exploited to gain complete system control. Attackers leveraging this flaw can execute arbitrary code with kernel privileges, potentially leading to full system compromise, data exfiltration, or persistent backdoor establishment. The vulnerability affects systems running Linux kernels version 6.6.7 and earlier, making it particularly concerning for enterprise environments that may still maintain legacy AppleTalk support or have not yet updated their kernel versions. The race condition aspect makes exploitation challenging to predict but also makes the vulnerability particularly dangerous as it can be triggered through normal network protocol operations.
Mitigation strategies for this vulnerability primarily focus on kernel version updates to 6.6.8 or later where the race condition has been addressed through proper synchronization mechanisms and memory management controls. System administrators should prioritize kernel updates across all affected systems, particularly those with AppleTalk protocol support enabled or those that might be exposed to network traffic that could trigger the vulnerable code path. Additional protective measures include implementing network segmentation to prevent unauthorized access to systems that might trigger the race condition, monitoring for unusual network activity related to AppleTalk protocols, and applying kernel hardening techniques such as stack canaries and address space layout randomization. This vulnerability aligns with CWE-416, which describes use-after-free conditions, and represents a significant risk under the ATT&CK framework's privilege escalation and execution techniques, particularly affecting the kernel execution domain. Organizations should also consider implementing automated patch management systems to ensure timely deployment of kernel security updates and establish monitoring protocols to detect potential exploitation attempts targeting kernel-level vulnerabilities.