CVE-2008-4539 in KVM
Summary
by MITRE
Heap-based buffer overflow in the Cirrus VGA implementation in (1) KVM before kvm-82 and (2) QEMU on Debian GNU/Linux and Ubuntu might allow local users to gain privileges by using the VNC console for a connection, aka the LGD-54XX "bitblt" heap overflow. NOTE: this issue exists because of an incorrect fix for CVE-2007-1320.
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Analysis
by VulDB Data Team • 08/20/2019
The CVE-2008-4539 vulnerability represents a critical heap-based buffer overflow within the Cirrus VGA graphics implementation of virtualization platforms, specifically affecting both KVM versions prior to kvm-82 and QEMU installations on Debian GNU/Linux and Ubuntu operating systems. This security flaw manifests through the VNC console connection mechanism, creating a pathway for local attackers to escalate their privileges within the virtualized environment. The vulnerability derives its name from the LGD-54XX "bitblt" heap overflow, indicating that the buffer overflow occurs during bitmap transfer operations within the graphics subsystem. The issue emerged as a result of an inadequate fix for CVE-2007-1320, demonstrating how remediation efforts can sometimes introduce new security weaknesses rather than resolving existing ones. This particular vulnerability resides in the virtual machine monitor layer where graphics rendering operations are processed, making it particularly dangerous as it operates within the hypervisor context.
The technical exploitation of this vulnerability occurs when a local user establishes a VNC connection to a virtual machine running on an affected system. During this connection process, the Cirrus VGA implementation processes graphics data through bitblt operations, which are fundamental graphics functions for copying blocks of data between memory regions. The heap-based buffer overflow specifically occurs when the system fails to properly validate the size of incoming graphics data during these bitblt operations, causing the program to write beyond allocated memory boundaries in the heap. This memory corruption can be leveraged to overwrite critical program data structures or execute arbitrary code with the privileges of the virtual machine process, which typically runs with elevated permissions. The vulnerability's classification as a heap overflow aligns with CWE-121, which describes heap-based buffer overflow conditions where insufficient bounds checking allows attackers to overwrite heap memory. The specific nature of this flaw places it within the ATT&CK framework under the technique of privilege escalation, specifically through exploitation of software vulnerabilities.
The operational impact of CVE-2008-4539 extends beyond simple local privilege escalation, as it can potentially allow attackers to compromise entire virtualized environments. In cloud computing and server virtualization deployments, where multiple virtual machines share the same physical host, this vulnerability creates a significant risk for multi-tenant environments. An attacker who successfully exploits this vulnerability could gain access to other virtual machines running on the same host, potentially leading to data breaches, service disruption, or further lateral movement within the infrastructure. The vulnerability affects systems where VNC console access is enabled, which represents a common configuration in virtualized environments for remote management and debugging purposes. Organizations using Debian GNU/Linux or Ubuntu distributions with affected QEMU installations face particular risk, as these platforms commonly serve as hypervisor environments for enterprise and cloud deployments. The fact that this vulnerability was introduced by a flawed fix for CVE-2007-1320 highlights the importance of thorough testing and validation of security patches, as improper remediation can create new attack vectors while appearing to address the original issue.
Mitigation strategies for CVE-2008-4539 focus primarily on updating the affected virtualization components to versions that contain proper fixes for the heap overflow vulnerability. System administrators should immediately upgrade their KVM installations to version kvm-82 or later, and ensure that QEMU packages are updated to versions that properly address the Cirrus VGA implementation flaw. Disabling VNC console access for virtual machines where it is not strictly required represents an additional defensive measure, as this eliminates the attack surface associated with the vulnerable graphics implementation. Organizations should also implement network segmentation to limit access to virtualization management interfaces, reducing the likelihood of exploitation. Monitoring for suspicious VNC connection patterns and implementing intrusion detection systems can help identify potential exploitation attempts. The vulnerability's presence in both KVM and QEMU environments emphasizes the need for comprehensive patch management across all virtualization components, as the fix must be applied consistently across the entire virtualization stack to provide complete protection. Additionally, organizations should conduct vulnerability assessments to identify other potential issues that may have been introduced by the flawed patch for CVE-2007-1320, ensuring that their virtualization infrastructure remains secure against similar remediation-related vulnerabilities.