CVE-2015-1333 in Linux
Summary
by MITRE
Memory leak in the __key_link_end function in security/keys/keyring.c in the Linux kernel before 4.1.4 allows local users to cause a denial of service (memory consumption) via many add_key system calls that refer to existing keys.
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Analysis
by VulDB Data Team • 06/07/2022
The vulnerability identified as CVE-2015-1333 represents a critical memory management flaw within the Linux kernel's key management subsystem. This issue resides in the __key_link_end function located in security/keys/keyring.c, where improper handling of key references leads to progressive memory consumption. The vulnerability affects Linux kernel versions prior to 4.1.4, making it a significant concern for systems running older kernel versions that have not received the necessary security patches.
The technical implementation of this flaw occurs when multiple add_key system calls are executed repeatedly, each referencing existing keys rather than creating new ones. The __key_link_end function fails to properly release memory resources associated with key references, causing a gradual accumulation of memory usage that eventually leads to system instability. This memory leak manifests as continuous memory consumption without corresponding deallocation, creating a condition where the system's available memory progressively decreases over time. The vulnerability specifically targets the kernel's keyring management mechanism, which is fundamental to the Linux security architecture for managing authentication tokens and credentials.
From an operational perspective, this vulnerability enables local attackers to perform a denial of service attack by continuously invoking add_key system calls that reference existing keys. The sustained memory consumption eventually exhausts available system memory, leading to system performance degradation or complete system crash. The impact extends beyond simple resource exhaustion as it affects the entire kernel's ability to manage security credentials effectively. This type of attack is particularly concerning because it requires minimal privileges and can be executed by any local user, making it a significant threat to system availability. The vulnerability aligns with CWE-401, which categorizes memory leaks as a common weakness in software security.
The attack vector for this vulnerability is straightforward and accessible to local users who can repeatedly invoke the add_key system call against existing key references. This approach allows for sustained memory consumption without requiring elevated privileges or complex exploitation techniques. The memory leak accumulates over time, making the impact more pronounced on systems that are continuously running or under heavy load. Security practitioners should note that this vulnerability can be detected through monitoring of memory consumption patterns and system performance metrics, particularly in environments where key management operations are frequent.
Mitigation strategies for CVE-2015-1333 primarily involve upgrading to Linux kernel version 4.1.4 or later, which contains the necessary patches to address the memory leak in the keyring subsystem. System administrators should prioritize kernel updates as part of their regular security maintenance procedures, especially given the local privilege escalation potential and denial of service implications. Additionally, monitoring system memory consumption and implementing automated alerts for unusual memory usage patterns can help detect exploitation attempts. The vulnerability demonstrates the importance of proper resource management in kernel code and highlights the necessity of thorough security testing for core system components. Organizations should also consider implementing access controls and monitoring for key management operations to limit potential exploitation opportunities. This vulnerability serves as a reminder of the critical nature of kernel security and the potential for seemingly minor memory management flaws to result in significant system stability issues. The ATT&CK framework would classify this vulnerability under privilege escalation and denial of service tactics, emphasizing the need for comprehensive kernel security hardening measures.