CVE-2001-0993 in NetBSD
Summary
by MITRE
sendmsg function in NetBSD 1.3 through 1.5 allows local users to cause a denial of service (kernel trap or panic) via a msghdr structure with a large msg_controllen length.
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Analysis
by VulDB Data Team • 05/31/2018
The vulnerability described in CVE-2001-0993 represents a critical kernel-level flaw in NetBSD operating systems version 1.3 through 1.5, specifically within the sendmsg system call implementation. This issue manifests as a denial of service condition that can result in either a kernel trap or complete system panic, fundamentally compromising system stability and availability. The vulnerability stems from inadequate input validation within the kernel's message handling mechanisms, where the system fails to properly sanitize the msg_controllen field of the msghdr structure. This particular field specifies the length of control information associated with a message, and when set to an excessively large value, it triggers memory corruption within the kernel's networking subsystem.
The technical exploitation of this vulnerability occurs when a local user crafts a malicious msghdr structure with an abnormally large msg_controllen value and passes it to the sendmsg system call. The kernel's failure to validate this parameter leads to improper memory allocation and handling, ultimately causing the kernel to crash or become unresponsive. This type of vulnerability falls under the Common Weakness Enumeration category of CWE-121, which deals with stack-based buffer overflow conditions, though in this case the overflow occurs within kernel memory management rather than user-space stack memory. The flaw demonstrates a classic case of insufficient bounds checking and input validation in kernel-level code, where the system assumes valid input without proper sanitization.
From an operational perspective, this vulnerability presents a significant risk to systems running affected NetBSD versions, as it allows any local user to potentially disrupt system services and cause complete system downtime. The impact extends beyond simple service disruption since a kernel panic can result in data loss, system instability, and require manual intervention for recovery. The vulnerability is particularly concerning because it requires no special privileges beyond local access, making it a low-barrier attack vector for malicious users who have already gained access to the system. Network services relying on socket communication would be directly impacted, as the sendmsg function is fundamental to network messaging operations, and any system crash would affect all network-dependent applications.
The mitigation strategies for this vulnerability primarily involve applying the appropriate security patches released by NetBSD developers, which would include proper bounds checking for the msg_controllen parameter within the sendmsg implementation. System administrators should prioritize updating affected systems to newer NetBSD versions where this vulnerability has been addressed. Additionally, implementing monitoring solutions to detect anomalous network behavior or system crashes can help identify exploitation attempts. Network segmentation and access controls can limit the potential impact by restricting local user access to systems running vulnerable versions. This vulnerability aligns with ATT&CK technique T1499.004, which involves network denial of service attacks, and demonstrates how kernel-level vulnerabilities can be leveraged to achieve system-level disruption. Organizations should also consider implementing kernel hardening measures and regularly auditing their system configurations to prevent exploitation of similar vulnerabilities in other kernel subsystems.