CVE-2017-11176 in Linux
Summary
by MITRE • 01/25/2023
The mq_notify function in the Linux kernel through 4.11.9 does not set the sock pointer to NULL upon entry into the retry logic. During a user-space close of a Netlink socket, it allows attackers to cause a denial of service (use-after-free) or possibly have unspecified other impact.
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Analysis
by VulDB Data Team • 12/28/2024
The vulnerability identified as CVE-2017-11176 resides within the Linux kernel's implementation of the mq_notify function, affecting kernel versions through 4.11.9. This flaw represents a critical security issue that stems from improper handling of socket pointers during error recovery scenarios. The vulnerability manifests when the mq_notify function enters its retry logic without properly nullifying the sock pointer, creating a dangerous condition that can be exploited by malicious actors. The root cause aligns with CWE-415, which addresses double free errors, and CWE-416, covering use-after-free conditions, both of which are fundamental memory safety vulnerabilities that can lead to system instability or arbitrary code execution.
The technical implementation of this vulnerability involves the mq_notify function's interaction with Netlink sockets, which are used for communication between user-space processes and the kernel. When a user-space application closes a Netlink socket, the kernel's retry logic path fails to properly clear the socket pointer reference. This creates a scenario where the socket structure may be freed from memory while still being referenced by the mq_notify function, leading to a use-after-free condition. The attacker can exploit this by carefully orchestrating socket operations that trigger the specific code path where the sock pointer remains non-null despite the socket being closed. This behavior violates the fundamental principle of proper resource management and memory lifecycle handling that should be enforced by the kernel's socket subsystem.
The operational impact of CVE-2017-11176 extends beyond simple denial of service, though that represents the primary immediate consequence. While the most common exploitation results in system crashes or reboot cycles due to memory corruption, the vulnerability's potential for more severe consequences cannot be ignored. The unspecified other impacts mentioned in the description suggest that under certain conditions, this vulnerability could enable privilege escalation or arbitrary code execution within the kernel context. This aligns with ATT&CK technique T1068, which covers local privilege escalation through kernel vulnerabilities, and represents a significant threat to system integrity. The vulnerability affects systems running Linux kernel versions up to 4.11.9, making it particularly concerning for enterprise environments that may still be running older kernel versions or have delayed patch deployment.
Mitigation strategies for CVE-2017-11176 primarily focus on kernel updates and system hardening measures. The most effective solution involves upgrading to a patched Linux kernel version that addresses the specific memory management issue in the mq_notify function's retry logic. Organizations should prioritize patch management processes to ensure all systems receive the appropriate kernel updates. Additionally, system administrators can implement monitoring solutions to detect unusual socket closure patterns that might indicate exploitation attempts. The vulnerability's nature suggests that defensive measures should include runtime protections such as kernel address space layout randomization and stack canaries, though these provide secondary protection rather than primary remediation. Network segmentation and privilege separation can help limit the potential impact if exploitation occurs, while regular system integrity checks and intrusion detection systems can aid in early detection of exploitation attempts. This vulnerability demonstrates the critical importance of proper resource management in kernel code and the severe consequences that can arise from inadequate pointer handling in concurrent access scenarios.