CVE-1999-1214 in BSD
Summary
by MITRE
The asynchronous I/O facility in 4.4 BSD kernel does not check user credentials when setting the recipient of I/O notification, which allows local users to cause a denial of service by using certain ioctl and fcntl calls to cause the signal to be sent to an arbitrary process ID.
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Analysis
by VulDB Data Team • 04/17/2026
The vulnerability described in CVE-1999-1214 represents a critical security flaw within the asynchronous I/O implementation of the 4.4 BSD kernel operating system. This issue stems from inadequate credential validation mechanisms within the kernel's I/O notification subsystem, specifically affecting how the system handles process identification for asynchronous I/O completion signals. The flaw exists in the kernel's handling of user-space requests to configure I/O notification recipients, creating a pathway for malicious local users to manipulate system behavior through improper privilege validation. The vulnerability is classified under CWE-284 which addresses improper access control mechanisms, specifically targeting the kernel's failure to validate user credentials when establishing I/O notification targets.
The technical implementation of this vulnerability exploits the asynchronous I/O facility's use of ioctl and fcntl system calls to configure notification recipients for I/O operations. When a local user invokes these system calls with malicious parameters, the kernel fails to validate whether the requesting user has appropriate privileges to direct I/O completion signals to arbitrary process identifiers. This credential bypass allows attackers to redirect I/O completion notifications to any process ID within the system, potentially causing cascading failures when legitimate processes receive unexpected signals. The vulnerability specifically affects the kernel's signal delivery mechanisms during asynchronous I/O operations, where process identifiers are accepted without proper authentication checks.
The operational impact of CVE-1999-1214 extends beyond simple denial of service conditions to potentially compromise system stability and integrity. Local users can leverage this vulnerability to disrupt normal system operations by causing legitimate processes to receive inappropriate signals, leading to application crashes, system hangs, or unexpected behavior. The attack vector requires only local access to the system, making it particularly dangerous as it can be exploited by any user with basic system privileges. The vulnerability can be particularly effective in multi-user environments where different processes may be running with varying privilege levels, allowing an attacker to target critical system processes or user applications for disruption.
Mitigation strategies for this vulnerability must address the fundamental credential validation flaw within the kernel's asynchronous I/O implementation. System administrators should implement immediate kernel updates and patches that correct the credential checking mechanisms for I/O notification recipients. The solution involves strengthening the kernel's privilege validation checks during ioctl and fcntl calls that configure asynchronous I/O completion signals, ensuring that only authorized processes can direct I/O notifications to specific recipients. Additionally, implementing proper access control lists and privilege separation mechanisms can help contain the impact of such vulnerabilities. From an ATT&CK framework perspective, this vulnerability maps to privilege escalation and denial of service tactics, requiring defensive measures that focus on kernel-level access control and process isolation. The vulnerability demonstrates the importance of proper input validation and credential checking in kernel space operations, aligning with security best practices that emphasize the principle of least privilege and comprehensive access control validation.