CVE-2015-3259 in Xen
Summary
by MITRE
Stack-based buffer overflow in the xl command line utility in Xen 4.1.x through 4.5.x allows local guest administrators to gain privileges via a long configuration argument.
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Analysis
by VulDB Data Team • 05/23/2022
The vulnerability identified as CVE-2015-3259 represents a critical stack-based buffer overflow flaw within the xl command line utility of the Xen hypervisor version 4.1.x through 4.5.x. This issue specifically affects local guest administrators who possess administrative privileges within virtual machines running on the affected Xen versions. The vulnerability arises from insufficient input validation when processing configuration arguments passed to the xl utility, creating an exploitable condition that can be leveraged for privilege escalation attacks. The flaw is particularly concerning because it allows attackers with guest administrator access to elevate their privileges to that of the host system, potentially compromising the entire virtualization environment.
The technical implementation of this vulnerability stems from improper bounds checking within the xl utility's argument parsing mechanism. When a maliciously crafted configuration argument exceeds the allocated stack buffer size, the overflow corrupts adjacent memory locations including return addresses and control data. This memory corruption enables attackers to manipulate the program execution flow and potentially execute arbitrary code with elevated privileges. The vulnerability is classified under CWE-121 as a stack-based buffer overflow, which occurs when data is copied to a stack buffer without proper size validation, leading to overwrite of adjacent stack memory. The attack vector requires local access to a guest VM with administrative privileges, making it a local privilege escalation vulnerability that can be particularly devastating in multi-tenant virtualization environments.
The operational impact of CVE-2015-3259 extends beyond simple privilege escalation, as it fundamentally undermines the security isolation that virtualization platforms are designed to provide. An attacker who successfully exploits this vulnerability can gain root-level access to the host system, potentially allowing them to access all virtual machines running on that host, extract sensitive data, modify system configurations, or establish persistent backdoors. This threat is particularly severe in cloud computing environments where multiple organizations share the same physical infrastructure, as a compromised guest VM could provide an attack surface for lateral movement across the entire platform. The vulnerability affects the core hypervisor functionality and can be exploited through the xl utility's configuration argument processing, making it difficult to detect and mitigate without proper patching or system hardening measures. According to ATT&CK framework, this vulnerability maps to privilege escalation techniques using local commands and arguments manipulation, specifically targeting the T1068 privilege escalation tactic.
Mitigation strategies for CVE-2015-3259 primarily focus on immediate patching of affected Xen versions to the latest stable releases that contain the necessary security fixes. System administrators should prioritize updating their Xen hypervisor installations to versions beyond 4.5.x where this vulnerability has been addressed. Additionally, implementing strict access controls and privilege separation within virtual environments can reduce the attack surface by limiting guest administrator permissions. Network segmentation and monitoring of xl utility usage can help detect anomalous behavior that might indicate exploitation attempts. The vulnerability also highlights the importance of input validation and secure coding practices in hypervisor components, as proper bounds checking and memory management would prevent the buffer overflow condition from occurring. Organizations should conduct comprehensive security assessments of their virtualization environments to identify and remediate similar vulnerabilities that may exist in other hypervisor management utilities. Regular security updates and vulnerability scanning should be implemented as part of the overall security posture to prevent exploitation of similar buffer overflow vulnerabilities in the hypervisor stack.