CVE-2005-2099 in Linux
Summary
by MITRE
The Linux kernel before 2.6.12.5 does not properly destroy a keyring that is not instantiated properly, which allows local users or remote attackers to cause a denial of service (kernel oops) via a keyring with a payload that is not empty, which causes the creation to fail, leading to a null dereference in the keyring destructor.
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Analysis
by VulDB Data Team • 06/11/2019
The vulnerability described in CVE-2005-2099 represents a critical flaw in the Linux kernel's keyring subsystem that existed in versions prior to 2.6.12.5. This issue stems from improper handling of keyring destruction when keyrings fail to instantiate correctly, creating a scenario where malformed keyring payloads can trigger kernel-level crashes. The vulnerability specifically affects the kernel's ability to manage security credentials and access control mechanisms that are fundamental to system security and integrity. Keyrings in Linux serve as containers for cryptographic keys and authentication tokens, making them essential components for maintaining secure system operations and access controls.
The technical flaw manifests when a keyring is created with a non-empty payload that causes the instantiation process to fail, resulting in a null pointer dereference during the keyring destructor execution. This occurs because the kernel's keyring management code does not properly validate the state of keyrings before attempting to destroy them, particularly when the keyring creation process encounters errors. The failure to handle this edge case leads to a kernel oops condition, which is a type of kernel panic that occurs when the kernel detects an abnormal condition that it cannot handle gracefully. This type of vulnerability falls under CWE-476 which specifically addresses null pointer dereference issues in software systems, making it particularly dangerous as it can be exploited to cause system instability.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be leveraged by both local users and remote attackers to disrupt system operations and potentially create conditions for more sophisticated attacks. When a kernel oops occurs, the system typically becomes unstable and may require a reboot to recover, effectively providing a denial of service attack vector that can be particularly damaging in server environments or systems where uptime is critical. The vulnerability's exploitation does not require elevated privileges for local users, making it accessible to any user with access to the system, while remote exploitation could be possible through network services that interact with the kernel's keyring subsystem. This aligns with ATT&CK technique T1499.004 which covers network denial of service attacks and demonstrates how kernel-level vulnerabilities can be weaponized for system disruption.
Mitigation strategies for this vulnerability involve upgrading to kernel versions 2.6.12.5 or later where the keyring destruction logic has been properly patched to handle null pointer scenarios. System administrators should also implement monitoring solutions to detect kernel oops events and ensure that security patches are applied promptly across all systems. Additional protective measures include restricting user access to keyring manipulation capabilities where possible and implementing proper system hardening practices to limit the attack surface. The fix implemented in the patched kernel versions ensures that keyring destructors properly validate keyring states before attempting cleanup operations, preventing the null pointer dereference that led to the original vulnerability. Organizations should also consider implementing automated patch management systems to ensure timely deployment of security updates and maintain comprehensive system logging to detect potential exploitation attempts.