CVE-2002-1490 in NetBSD
Summary
by MITRE
NetBSD 1.4 through 1.6 beta allows local users to cause a denial of service (kernel panic) via a series of calls to the TIOCSCTTY ioctl, which causes an integer overflow in a structure counter and sets the counter to zero, which frees memory that is still in use by other processes.
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Analysis
by VulDB Data Team • 06/13/2018
The vulnerability described in CVE-2002-1490 represents a critical kernel-level flaw affecting NetBSD versions 1.4 through 1.6 beta releases. This issue stems from improper handling of the TIOCSCTTY ioctl system call which is used to control terminal characteristics and establish controlling terminals for processes. The vulnerability operates at the kernel level where memory management and process control intersect, creating a dangerous condition that can be exploited by local users to trigger system-wide disruptions.
The technical root cause of this vulnerability lies in an integer overflow condition that occurs within the kernel's handling of terminal control structures. When multiple TIOCSCTTY ioctl calls are made in sequence, the internal counter used to track terminal associations undergoes an integer overflow, causing it to wrap around to zero. This seemingly simple arithmetic error has catastrophic consequences as it leads to premature memory deallocation. The kernel's memory management subsystem attempts to free memory that is still actively referenced by other processes, creating a scenario where freed memory is accessed by concurrent processes, resulting in kernel panics and system crashes.
This vulnerability directly maps to CWE-190, which specifically addresses integer overflow conditions that can lead to memory corruption and system instability. The flaw demonstrates how seemingly benign ioctl operations can be weaponized to exploit fundamental kernel memory management principles. From an operational perspective, this vulnerability represents a significant threat to system availability as local users can reliably trigger kernel panics without requiring elevated privileges, making it particularly dangerous in multi-user environments where users might have legitimate access to terminal control operations.
The impact of this vulnerability extends beyond simple denial of service, as kernel panics can result in complete system crashes, data loss, and potential compromise of system integrity. Attackers can repeatedly exploit this flaw to maintain persistent denial of service conditions, effectively rendering affected systems unusable. The vulnerability also presents indirect security implications as kernel panics can be leveraged to mask other malicious activities or create opportunities for privilege escalation attacks. Organizations running affected NetBSD versions should prioritize immediate patching or implementation of compensating controls to prevent exploitation.
The ATT&CK framework categorizes this vulnerability under T1499, which covers network denial of service attacks, and T1068, which addresses exploits for privilege escalation. This classification reflects how local users can leverage kernel-level flaws to achieve system-wide disruption. The vulnerability's exploitation requires minimal privileges and can be automated, making it particularly attractive to threat actors seeking to disrupt services. System administrators should implement monitoring for unusual ioctl call patterns and establish robust patch management processes to address this and similar kernel-level vulnerabilities. The incident highlights the critical importance of proper integer overflow handling in kernel code and demonstrates how memory safety issues in core operating system components can have far-reaching consequences for overall system security and reliability.