CVE-2005-2098 in Linux
Summary
by MITRE
The KEYCTL_JOIN_SESSION_KEYRING operation in the Linux kernel before 2.6.12.5 contains an error path that does not properly release the session management semaphore, which allows local users or remote attackers to cause a denial of service (semaphore hang) via a new session keyring (1) with an empty name string, (2) with a long name string, (3) with the key quota reached, or (4) ENOMEM.
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Analysis
by VulDB Data Team • 07/04/2019
The vulnerability described in CVE-2005-2098 represents a critical flaw in the Linux kernel's key management subsystem that affects versions prior to 2.6.12.5. This issue specifically targets the KEYCTL_JOIN_SESSION_KEYRING operation which is part of the kernel's security framework responsible for managing session keyrings. The vulnerability arises from improper resource management during error handling paths within the kernel's key management code, creating a scenario where essential system resources remain locked indefinitely. The flaw manifests when the kernel encounters specific error conditions during session keyring creation, particularly when dealing with malformed or resource-constrained inputs.
The technical implementation of this vulnerability involves the kernel's session management semaphore mechanism, which is designed to ensure exclusive access to session keyring operations. When certain error conditions occur during the KEYCTL_JOIN_SESSION_KEYRING operation, the kernel fails to properly release this semaphore, leading to a deadlock condition. The vulnerability can be triggered through four distinct attack vectors: creation of a session keyring with an empty name string, use of a long name string that exceeds buffer limits, attempts to create keyrings when the key quota has been reached, and scenarios where memory allocation fails with ENOMEM errors. Each of these conditions represents a different code path that fails to execute proper cleanup procedures for the semaphore, demonstrating poor defensive programming practices in kernel space.
The operational impact of this vulnerability is severe and directly translates to a denial of service condition that can effectively hang the system or render key management operations unavailable. When the semaphore remains locked due to incomplete error handling, legitimate processes attempting to create or manage session keyrings will block indefinitely, causing system instability and potential service disruption. This vulnerability affects both local users who can exploit it to cause system hangs and remote attackers who may leverage it in network-based attacks against systems running vulnerable kernel versions. The denial of service impact extends beyond simple system unresponsiveness as it can compromise the entire security framework's ability to manage cryptographic keys and authentication tokens, which are fundamental to system security operations.
From a security standards perspective, this vulnerability maps directly to CWE-665 Improper Initialization and CWE-775 Missing Release of Resource after Effective Lifetime, both of which are classified under the broader category of resource management flaws. The issue also aligns with ATT&CK technique T1499.004 for Network Denial of Service and T1068 for Exploitation for Privilege Escalation, as local users can potentially leverage the denial of service condition to gain further system access. The vulnerability demonstrates a classic example of how improper error handling in kernel space can lead to system-wide stability issues and represents a failure in the kernel's resource management protocols. The fix for this vulnerability required implementing proper semaphore release mechanisms in all error paths of the key management subsystem, ensuring that system resources are always properly cleaned up regardless of execution flow.
Mitigation strategies for CVE-2005-2098 include immediate patching of all affected systems to kernel version 2.6.12.5 or later, where the vulnerability has been addressed through proper error handling implementation. Organizations should also implement monitoring for unusual semaphore usage patterns and system hang conditions that may indicate exploitation attempts. System administrators should consider implementing additional security controls around key management operations and ensure that all kernel updates are applied promptly. The vulnerability serves as a reminder of the critical importance of proper resource management in kernel space and the potential for seemingly minor error handling flaws to create significant system stability issues. Regular security assessments of kernel components and comprehensive testing of error paths in security-critical subsystems remain essential practices to prevent similar vulnerabilities from emerging in future system deployments.