CVE-2005-4639 in Linux
Summary
by MITRE
Buffer overflow in the CA-driver (dst_ca.c) for TwinHan DST Frontend/Card in Linux kernel 2.6.12 and other versions before 2.6.15 allows local users to cause a denial of service (crash) and possibly execute arbitrary code by "reading more than 8 bytes into an 8 byte long array".
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Analysis
by VulDB Data Team • 07/25/2019
The vulnerability identified as CVE-2005-4639 represents a critical buffer overflow flaw within the Linux kernel's TwinHan DST Frontend/Card driver implementation. This issue specifically affects the CA-driver component known as dst_ca.c which handles communication with conditional access modules in digital satellite television receivers. The vulnerability exists in kernel versions prior to 2.6.15, making it particularly concerning as it impacted a substantial portion of the Linux kernel ecosystem during that time period. The flaw manifests when the driver processes data from external sources without proper bounds checking, creating a scenario where malicious input can exceed the allocated buffer space.
The technical nature of this vulnerability stems from improper input validation within the dst_ca.c driver file where a fixed 8-byte array is allocated to handle incoming data. When local users attempt to read more than 8 bytes into this constrained buffer, the excess data overflows into adjacent memory locations, potentially corrupting critical system data structures. This buffer overflow condition creates a situation where the kernel's memory management becomes compromised, leading to unpredictable behavior and system instability. The vulnerability operates at the kernel level, meaning that exploitation can result in complete system compromise. According to CWE classification, this represents a classic buffer overflow vulnerability (CWE-121) that falls under the category of heap-based buffer overflows, though it specifically manifests in stack-based contexts due to the local nature of the attack vector.
The operational impact of CVE-2005-4639 extends beyond simple denial of service scenarios, as the vulnerability presents a potential path for privilege escalation and arbitrary code execution. Local attackers who can access the system can leverage this flaw to crash the kernel or potentially execute malicious code with kernel-level privileges, which would provide complete control over the affected system. The nature of the TwinHan DST Frontend/Card hardware makes this vulnerability particularly relevant in digital satellite receiver environments where such devices are commonly deployed. The vulnerability's exploitation requires local access, but the potential for privilege escalation means that even limited user access could result in complete system compromise. The attack surface is broad as it affects all systems running affected kernel versions, making it a high-priority vulnerability for system administrators to address immediately.
Mitigation strategies for this vulnerability primarily involve applying the appropriate kernel security patches released by the Linux kernel development team as part of the 2.6.15 release cycle. System administrators should prioritize upgrading to kernel versions 2.6.15 or later where the buffer overflow has been addressed through proper bounds checking implementation. Additionally, implementing kernel security modules such as grsecurity or PaX can provide additional protection layers against buffer overflow attacks by introducing stack canaries, non-executable stack protections, and other memory protection mechanisms. The vulnerability highlights the importance of input validation in kernel space code and underscores the necessity of thorough security testing for device drivers. Organizations should also consider implementing network segmentation and access controls to limit local user access to systems running vulnerable kernel versions, thereby reducing the attack surface for exploitation attempts. This vulnerability serves as a reminder of the critical importance of maintaining up-to-date kernel versions and proper security practices in embedded systems environments where kernel-level vulnerabilities can have severe operational consequences.