CVE-2008-3584 in NetBSD
Summary
by MITRE
NetBSD 3.0, 3.1, and 4.0, when a pppoe instance exists, does not properly check the length of a PPPoE packet tag, which allows remote attackers to cause a denial of service (system crash) via a crafted PPPoE packet.
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Analysis
by VulDB Data Team • 08/02/2021
The vulnerability described in CVE-2008-3584 represents a critical buffer over-read condition within the NetBSD operating system's implementation of the Point-to-Point Protocol over Ethernet (PPPoE) functionality. This flaw exists in NetBSD versions 3.0, 3.1, and 4.0 where the system fails to properly validate the length of PPPoE packet tags during processing. The vulnerability specifically manifests when the PPPoE subsystem encounters a malformed packet containing oversized or improperly formatted tags, leading to a potential system crash and denial of service condition. This issue falls under the CWE-129 vulnerability category, which encompasses improper validation of buffer bounds, and demonstrates a classic example of how insufficient input validation can lead to system instability. The flaw operates at the network protocol level where the kernel's PPPoE driver does not adequately sanitize packet metadata before processing, creating a pathway for malicious actors to exploit the system's memory management routines.
The technical execution of this vulnerability requires an attacker to craft and transmit a specially formatted PPPoE packet that contains tags with lengths exceeding the expected boundaries. When the NetBSD kernel processes such a packet, the insufficient length validation causes the system to attempt to read beyond allocated memory boundaries, resulting in a kernel panic or system crash. This type of exploitation aligns with ATT&CK technique T1499.004, which covers network denial of service attacks through malformed packets, and demonstrates how protocol-level vulnerabilities can be leveraged to achieve system-level compromise. The vulnerability is particularly concerning because it operates at the kernel level, meaning that successful exploitation results in complete system instability rather than merely application-level disruption. The flaw essentially creates a condition where the kernel's memory management subsystem receives malformed data that causes it to access invalid memory locations, triggering a system crash that can be reliably reproduced through network-based attacks.
The operational impact of CVE-2008-3584 extends beyond simple denial of service, as it represents a fundamental security weakness that could potentially be exploited as a stepping stone for more sophisticated attacks. Systems running affected NetBSD versions that are exposed to untrusted network traffic become vulnerable to remote exploitation, potentially allowing attackers to disrupt network services or gain unauthorized access to system resources. The vulnerability affects network infrastructure devices and servers that utilize PPPoE connections, making it particularly dangerous in environments where such connections are common, such as internet service provider networks or enterprise environments using PPPoE for remote access. Organizations running these vulnerable versions of NetBSD should consider the broader implications of this vulnerability, as it demonstrates poor input validation practices that could indicate similar weaknesses in other kernel subsystems. The flaw also highlights the importance of proper memory bounds checking in kernel code, as outlined in various security frameworks that emphasize the need for defensive programming practices to prevent buffer overflows and related memory corruption vulnerabilities.
Mitigation strategies for this vulnerability primarily focus on applying the appropriate security patches and updates provided by NetBSD developers. System administrators should immediately upgrade to NetBSD versions that contain fixes for this vulnerability, as the official releases include proper bounds checking for PPPoE packet tags. Network administrators can also implement additional protective measures such as configuring network access control lists to filter out suspicious PPPoE traffic or deploying network monitoring systems to detect anomalous packet patterns that might indicate exploitation attempts. The vulnerability serves as a reminder of the critical importance of maintaining up-to-date system software and the need for comprehensive security testing of network protocol implementations. Organizations should also consider implementing intrusion detection systems that can identify and alert on malformed PPPoE packets, as well as conducting regular security audits of network infrastructure components to identify and remediate similar vulnerabilities in other system components. Proper input validation and bounds checking should be enforced throughout kernel code to prevent similar issues from arising in future implementations, following established security best practices and standards.