CVE-2011-1763 in Xen
Summary
by MITRE
The get_free_port function in Xen allows local authenticated DomU users to cause a denial of service or possibly gain privileges via unspecified vectors involving a new event channel port.
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Analysis
by VulDB Data Team • 01/18/2022
The CVE-2011-1763 vulnerability resides within the Xen hypervisor's get_free_port function, representing a critical security flaw that affects virtualized environments. This vulnerability specifically targets DomU domains, which are unprivileged virtual machines running on top of the Xen hypervisor. The issue stems from insufficient validation mechanisms within the event channel port allocation process, creating opportunities for malicious local users to exploit the system. The vulnerability's impact extends beyond simple denial of service, as it potentially allows privilege escalation through unspecified attack vectors that manipulate the event channel port management system. Event channels serve as the primary communication mechanism between hypervisor and guest domains, making this flaw particularly dangerous in virtualized environments where multiple domains share the same physical hardware.
The technical exploitation of this vulnerability occurs through the manipulation of event channel port allocation within the Xen hypervisor's kernel space. When a DomU domain requests a new event channel port, the get_free_port function fails to properly validate or sanitize the port allocation request. This flaw enables authenticated local users to potentially exhaust available port resources or manipulate port assignments in ways that could lead to system instability. The unspecified vectors mentioned in the description suggest that attackers might leverage multiple approaches including port exhaustion attacks, race condition exploitation, or memory corruption techniques. These methods could result in the hypervisor crashing or allowing unauthorized privilege elevation, depending on the specific implementation details and attack surface. The vulnerability demonstrates poor input validation and resource management practices that align with CWE-129, which covers insufficient validation of the length of input data, and CWE-362, addressing concurrent execution using shared resources.
The operational impact of CVE-2011-1763 extends significantly beyond immediate service disruption, as it undermines the fundamental security model of virtualized environments. In production systems, this vulnerability could allow malicious users within a DomU to either crash the entire hypervisor, causing cascading failures across all virtual machines hosted on that physical system, or potentially escalate their privileges to gain unauthorized access to the host system. The implications are particularly severe in cloud computing environments where multiple tenants share the same infrastructure, as a single compromised DomU could affect the entire platform. Network administrators and security teams must consider that this vulnerability could be exploited to create persistent backdoors or to compromise the integrity of the entire virtualization stack. The attack vector's local nature means that physical access or legitimate system access is required, but the potential for privilege escalation makes this a critical concern for systems where guest users might have elevated access rights. This vulnerability also aligns with ATT&CK technique T1068, which covers local privilege escalation, and T1499, addressing network denial of service.
Mitigation strategies for CVE-2011-1763 require immediate patching of affected Xen hypervisor versions, as the vulnerability represents a fundamental flaw in the kernel's resource management system. System administrators should implement strict access controls and monitoring for event channel port usage, particularly in environments where multiple DomU domains are present. The recommended approach includes upgrading to patched Xen versions that address the specific port allocation validation issues and implementing additional logging mechanisms to detect unusual port allocation patterns. Organizations should also consider implementing network segmentation and access control lists to limit the potential impact of a successful exploitation attempt. Regular security assessments and vulnerability scanning should include checks for proper event channel port management and resource allocation validation. The remediation process should involve comprehensive testing of patched systems to ensure that the vulnerability has been fully addressed without introducing regressions in system functionality. Additionally, implementing proper audit logging for hypervisor operations and establishing incident response procedures specifically for virtualization-related security incidents will help organizations respond effectively to potential exploitation attempts.