CVE-2017-12193 in Linux
Summary
by MITRE
The assoc_array_insert_into_terminal_node function in lib/assoc_array.c in the Linux kernel before 4.13.11 mishandles node splitting, which allows local users to cause a denial of service (NULL pointer dereference and panic) via a crafted application, as demonstrated by the keyring key type, and key addition and link creation operations.
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Analysis
by VulDB Data Team • 01/11/2023
The vulnerability identified as CVE-2017-12193 resides within the Linux kernel's associative array implementation, specifically in the assoc_array_insert_into_terminal_node function located in lib/assoc_array.c. This flaw affects kernel versions prior to 4.13.11 and represents a critical denial of service vulnerability that can be exploited by local attackers through carefully crafted applications. The issue stems from improper handling of node splitting operations within the associative array data structure, which is utilized extensively throughout the kernel for various purposes including keyring management and other internal data organization tasks.
The technical root cause of this vulnerability lies in the insufficient validation and handling of memory allocation scenarios during the node splitting process. When the associative array encounters conditions requiring node splitting, the assoc_array_insert_into_terminal_node function fails to properly manage the memory references, leading to a situation where a NULL pointer dereference occurs during subsequent keyring operations. This particular flaw manifests when applications attempt to perform key addition and link creation operations through the keyring key type interface, which internally relies on the problematic associative array implementation. The vulnerability demonstrates a classic case of improper error handling in kernel space where the failure to properly manage memory allocation states during data structure modifications creates a path for system crashes.
The operational impact of CVE-2017-12193 extends beyond simple system instability, as it can be leveraged by local malicious users to induce kernel panics and complete system denial of service. The vulnerability's exploitation requires only local privileges and does not necessitate network access or specialized external conditions, making it particularly concerning for systems where local user access is possible. When successfully exploited, the vulnerability causes immediate system crashes that can result in complete system downtime, requiring manual intervention for recovery and potentially leading to data loss in environments where such crashes occur during critical operations. The keyring subsystem, which is fundamental to Linux security infrastructure for managing authentication tokens and credentials, becomes particularly vulnerable, potentially compromising the security posture of affected systems.
This vulnerability aligns with CWE-476, which describes NULL pointer dereference conditions, and represents a specific instance where improper memory management in kernel data structures leads to system instability. From an ATT&CK framework perspective, this vulnerability maps to T1499.004, covering network denial of service, though it operates in a local context rather than network-based. The flaw also demonstrates characteristics of T1068, which involves local privilege escalation opportunities, as local users can exploit it to cause system-wide disruptions. Mitigation strategies should focus on immediate kernel version updates to 4.13.11 or later, where the node splitting logic has been corrected to properly handle memory allocation states. System administrators should also consider implementing additional monitoring for unusual kernel panic patterns and ensure that keyring operations are properly audited for potential exploitation attempts. The vulnerability serves as a reminder of the critical importance of proper memory management in kernel space and the potential for seemingly minor implementation flaws to result in significant system stability issues.