CVE-2009-1758 in Xen
Summary
by MITRE
The hypervisor_callback function in Xen, possibly before 3.4.0, as applied to the Linux kernel 2.6.30-rc4, 2.6.18, and probably other versions allows guest user applications to cause a denial of service (kernel oops) of the guest OS by triggering a segmentation fault in "certain address ranges."
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Analysis
by VulDB Data Team • 09/06/2019
The vulnerability identified as CVE-2009-1758 represents a critical flaw in the Xen hypervisor implementation that affects virtualized environments running Linux kernel versions 2.6.30-rc4, 2.6.18, and potentially other versions. This issue stems from improper handling of memory addresses within the hypervisor_callback function, creating a pathway for malicious guest applications to exploit the virtualization layer and disrupt guest operating system functionality. The vulnerability specifically targets the interaction between the hypervisor and guest operating systems, where guest user applications can manipulate memory access patterns to trigger kernel oops conditions that result in system instability.
The technical flaw manifests when guest applications attempt to access certain memory address ranges that are not properly validated or protected by the hypervisor. This allows attackers to trigger segmentation faults that propagate through the virtualization layer, causing the guest operating system to crash or become unresponsive. The hypervisor_callback function, which serves as an interface between the hypervisor and guest operating systems, fails to adequately sanitize memory access requests from untrusted guest applications. This vulnerability falls under the CWE-125 vulnerability category, which deals with out-of-bounds read conditions, and represents a classic case of improper input validation in virtualization software components.
The operational impact of this vulnerability extends beyond simple denial of service, as it can be exploited to cause complete system crashes within virtualized environments. Guest operating systems running on affected Xen versions become vulnerable to malicious code execution that can disrupt service availability, potentially affecting multiple virtual machines sharing the same physical host. Attackers can leverage this vulnerability to cause persistent disruptions to virtualized services, making it particularly dangerous in cloud computing environments where multiple tenants share the same infrastructure. The vulnerability also poses risks to system administrators who may not immediately recognize the source of intermittent system failures, as the symptoms manifest as kernel oops conditions that can be difficult to trace back to the hypervisor layer.
Mitigation strategies for CVE-2009-1758 require immediate patching of affected Xen versions, with the recommended solution being upgrade to Xen 3.4.0 or later where the vulnerability has been addressed through improved memory access validation in the hypervisor_callback function. System administrators should also implement monitoring solutions that can detect unusual kernel oops patterns and segmentation fault occurrences that may indicate exploitation attempts. Additional defensive measures include implementing strict virtual machine resource controls to limit the ability of guest applications to access memory regions that could trigger the vulnerability, and ensuring that all virtualized environments undergo regular security assessments to identify similar flaws in hypervisor implementations. The ATT&CK framework categorizes this vulnerability under the T1499 sub-technique for Network Denial of Service, as the exploitation results in service disruption that affects the availability of virtualized computing resources.