CVE-2006-4623 in Linux
Summary
by MITRE
The Unidirectional Lightweight Encapsulation (ULE) decapsulation component in dvb-core/dvb_net.c in the dvb driver in the Linux kernel 2.6.17.8 allows remote attackers to cause a denial of service (crash) via an SNDU length of 0 in a ULE packet.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 07/09/2019
The vulnerability identified as CVE-2006-4623 resides within the Linux kernel's Digital Video Broadcasting driver subsystem, specifically in the dvb-core/dvb_net.c module. This flaw affects kernel version 2.6.17.8 and represents a critical denial of service vulnerability that can be exploited remotely through crafted network packets. The issue manifests in the Unidirectional Lightweight Encapsulation decapsulation component which processes incoming ULE packets destined for digital video broadcasting applications. The vulnerability stems from inadequate input validation within the packet processing logic, creating a scenario where malformed packets can trigger system instability.
The technical flaw occurs when the ULE decapsulation routine encounters a packet with an SNDU (Simplified Network Data Unit) length field set to zero. This condition bypasses normal validation checks that should occur during packet parsing, allowing the kernel to attempt processing of a malformed data structure. The zero-length SNDU value creates a condition where the kernel's memory management routines receive invalid parameters, leading to improper memory access patterns and ultimately resulting in kernel crashes. This represents a classic buffer over-read or invalid memory dereference vulnerability that falls under the CWE-125 weakness category for out-of-bounds read conditions.
From an operational perspective, this vulnerability presents significant risks to systems utilizing Linux-based digital video broadcasting equipment, particularly those deployed in network infrastructure or embedded devices. Attackers can remotely trigger system crashes by sending specially crafted ULE packets with zero-length SNDU fields, potentially disrupting services for extended periods. The impact extends beyond simple service interruption as these crashes can affect critical infrastructure components such as set-top boxes, satellite receivers, and network gateways. The vulnerability's remote exploitability means that attackers do not need physical access to the target system, making it particularly dangerous for publicly accessible broadcasting equipment.
The mitigation strategies for CVE-2006-4623 primarily involve applying the official kernel patch released by the Linux kernel development team, which implements proper validation of SNDU length fields during packet processing. System administrators should also consider implementing network-level filtering to block malformed ULE packets at network boundaries, particularly in environments where such traffic is not expected. Additionally, monitoring systems should be configured to detect unusual patterns of kernel crashes or system restarts that might indicate exploitation attempts. The vulnerability demonstrates the importance of proper input validation in kernel space code and aligns with ATT&CK technique T1499.004 for network disruption through resource exhaustion or system crashes. Organizations should also implement regular kernel updates and security assessments to prevent similar vulnerabilities from being exploited in their digital broadcasting infrastructure.