CVE-2016-4580 in Linux
Summary
by MITRE
The x25_negotiate_facilities function in net/x25/x25_facilities.c in the Linux kernel before 4.5.5 does not properly initialize a certain data structure, which allows attackers to obtain sensitive information from kernel stack memory via an X.25 Call Request.
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Analysis
by VulDB Data Team • 08/22/2022
The vulnerability identified as CVE-2016-4580 resides within the Linux kernel's X.25 networking implementation, specifically in the x25_negotiate_facilities function located in net/x25/x25_facilities.c. This flaw represents a classic information disclosure vulnerability that arises from improper initialization of kernel data structures. The X.25 protocol is a legacy packet-switched network protocol that was widely used in telecommunications networks, particularly in the 1970s and 1980s, though it continues to be relevant in certain specialized networking environments. The vulnerability manifests when an X.25 Call Request is processed, triggering the function that fails to properly initialize a critical data structure before use.
The technical root cause of this vulnerability stems from a failure to properly initialize memory structures within the kernel space, creating a situation where sensitive data from the kernel stack may be inadvertently exposed to userspace applications. This occurs because the x25_negotiate_facilities function does not adequately clear or initialize memory regions before populating them with data from incoming X.25 Call Request packets. The uninitialized data structure contains remnants of previous kernel operations, potentially including cryptographic keys, session tokens, or other sensitive information that should not be accessible to unprivileged users. This type of vulnerability falls under CWE-119 which describes improper access to memory locations, specifically uninitialized memory access patterns that lead to information disclosure.
The operational impact of CVE-2016-4580 is significant within environments that utilize X.25 networking protocols, particularly in legacy telecommunications systems, industrial control networks, or specialized networking infrastructure where such protocols remain in active use. An attacker who can send an X.25 Call Request to a vulnerable system can potentially extract sensitive information from kernel memory, which could include system configuration details, authentication tokens, cryptographic material, or other confidential data that may be stored in the kernel stack. This information disclosure could enable further attacks, including privilege escalation, system compromise, or targeted attacks against specific network components. The vulnerability is particularly concerning because it operates at the kernel level, meaning that even unprivileged users can exploit it to gain access to kernel memory contents.
From a cybersecurity framework perspective, this vulnerability aligns with several ATT&CK techniques including T1005 (Data from Local System) and T1059 (Command and Scripting Interpreter) as it enables attackers to extract sensitive data from system memory. The vulnerability also represents a failure in the principle of least privilege, as it allows unauthorized access to kernel memory spaces that should remain protected from user-space processes. Organizations utilizing Linux systems in environments where X.25 networking is active should prioritize patching this vulnerability, as it represents a potential backdoor for attackers to gather intelligence about the target system. The recommended mitigation involves upgrading to Linux kernel version 4.5.5 or later, where the memory initialization issue has been corrected. Additionally, network segmentation and monitoring of X.25 traffic can help detect potential exploitation attempts, while implementing proper access controls and privilege separation can reduce the overall risk surface. This vulnerability underscores the importance of proper memory management practices in kernel code and highlights the need for thorough security testing of network protocol implementations, particularly in legacy systems that continue to receive security updates and patches.