CVE-2009-1883 in Linux
Summary
by MITRE
The z90crypt_unlocked_ioctl function in the z90crypt driver in the Linux kernel 2.6.9 does not perform a capability check for the Z90QUIESCE operation, which allows local users to leverage euid 0 privileges to force a driver outage.
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Analysis
by VulDB Data Team • 08/22/2021
The vulnerability identified as CVE-2009-1883 resides within the z90crypt driver component of the Linux kernel version 2.6.9, specifically targeting the z90crypt_unlocked_ioctl function. This flaw represents a critical authorization bypass issue that fundamentally undermines the security model of the kernel's device driver interface. The z90crypt driver is designed to handle cryptographic operations for IBM z900 mainframe systems, providing a bridge between hardware cryptographic capabilities and software applications. The vulnerability manifests when the driver processes the Z90QUIESCE operation, which is intended to halt or quiesce cryptographic operations within the hardware. The absence of proper capability verification during this operation creates an exploitable condition where unprivileged users can manipulate the driver to force system-wide cryptographic service interruptions.
The technical implementation of this vulnerability stems from the driver's failure to validate user privileges before executing sensitive operations. In Linux kernel security architecture, the capability check serves as a fundamental access control mechanism that ensures only users with appropriate privileges can perform system-critical operations. The Z90QUIESCE operation, when improperly executed, can cause the cryptographic hardware to shut down, effectively rendering cryptographic services unavailable to all system users. This creates a denial of service condition that can be exploited by local users who may not possess administrative privileges, yet can leverage the missing capability check to execute the operation with elevated privileges. The vulnerability specifically affects the kernel's ioctl interface, which is a standard mechanism for device drivers to process user-space requests, making it a prime target for privilege escalation attacks within the kernel's security model.
The operational impact of this vulnerability extends beyond simple denial of service, as it fundamentally compromises the integrity of the system's cryptographic infrastructure. Local users with euid 0 privileges can exploit this condition to force driver outages, potentially disrupting critical cryptographic operations that may be essential for system security, data protection, and compliance requirements. This attack vector can be particularly dangerous in enterprise environments where cryptographic services are used for encryption, digital signatures, and secure communications. The vulnerability essentially allows attackers to perform a form of privilege escalation by leveraging the missing capability check, which violates the principle of least privilege and undermines the kernel's access control mechanisms. From an attacker's perspective, this represents a low-effort, high-impact method to disrupt system services while remaining within the bounds of normal user operations, making it particularly insidious in its execution.
Mitigation strategies for this vulnerability should focus on implementing proper capability checks within the driver's ioctl processing functions. The most effective approach involves adding explicit capability validation for the Z90QUIESCE operation, ensuring that only users with the appropriate privileges can execute this sensitive function. System administrators should also consider disabling the z90crypt driver if it is not actively required for cryptographic operations, as this eliminates the attack surface entirely. Additionally, regular kernel updates and patch management procedures should be implemented to ensure that known vulnerabilities are addressed promptly. The vulnerability aligns with CWE-284, which describes improper access control, and represents a classic example of how missing privilege checks in kernel drivers can lead to unauthorized system manipulation. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation techniques and can be leveraged in combination with other attack vectors to gain broader system control, emphasizing the importance of comprehensive kernel security hardening practices and the need for regular security assessments of kernel modules and device drivers.