CVE-2007-4993 in Xen
Summary
by MITRE
pygrub (tools/pygrub/src/GrubConf.py) in Xen 3.0.3, when booting a guest domain, allows local users with elevated privileges in the guest domain to execute arbitrary commands in domain 0 via a crafted grub.conf file whose contents are used in exec statements.
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Analysis
by VulDB Data Team • 01/04/2025
The vulnerability identified as CVE-2007-4993 represents a critical privilege escalation flaw within the Xen virtualization platform's pygrub component. This issue affects Xen version 3.0.3 and specifically targets the guest domain boot process where pygrub is responsible for parsing grub.conf configuration files. The vulnerability stems from insufficient input validation and sanitization of grub.conf file contents, creating a command injection vector that can be exploited by malicious actors with elevated privileges within a guest domain.
The technical exploitation occurs through the manipulation of grub.conf files that contain specially crafted content designed to trigger execution of arbitrary commands within the privileged domain 0 context. When pygrub processes these malicious configuration files, it inadvertently passes user-controlled data into exec statements without proper sanitization, allowing attackers to execute arbitrary code with the elevated privileges of domain 0. This represents a classic command injection vulnerability that violates fundamental security principles of input validation and privilege separation within virtualized environments.
The operational impact of this vulnerability is severe as it allows local users within a guest domain to escalate their privileges to the highest level of the Xen hypervisor, effectively compromising the entire virtualization infrastructure. Domain 0 serves as the privileged management domain in Xen architectures, and compromising its security undermines the fundamental isolation guarantees that virtualization provides. This vulnerability essentially breaks the security boundary between guest domains and the hypervisor, enabling attackers to gain complete control over the host system and all virtual machines running on it.
This vulnerability maps directly to CWE-78, which describes improper neutralization of special elements used in OS commands, and aligns with ATT&CK technique T1059.001 for command and scripting interpreter. The flaw demonstrates poor input validation practices and highlights the importance of secure coding principles in hypervisor components. Organizations should implement immediate mitigations including patching to newer Xen versions, restricting guest domain privileges, and implementing strict file access controls on grub.conf files. Additionally, monitoring for suspicious command execution patterns and implementing principle of least privilege for guest domain users can help reduce the attack surface and prevent exploitation of this critical vulnerability.