CVE-2015-5225 in QEMU
Summary
by MITRE
Buffer overflow in the vnc_refresh_server_surface function in the VNC display driver in QEMU before 2.4.0.1 allows guest users to cause a denial of service (heap memory corruption and process crash) or possibly execute arbitrary code on the host via unspecified vectors, related to refreshing the server display surface.
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Analysis
by VulDB Data Team • 06/15/2022
The vulnerability CVE-2015-5225 represents a critical buffer overflow flaw in the QEMU virtualization platform's VNC display driver component. This issue exists within the vnc_refresh_server_surface function which handles the refreshing of the server display surface during virtual machine operations. The vulnerability affects QEMU versions prior to 2.4.0.1 and demonstrates a classic heap-based buffer overflow condition that can be exploited by authenticated guest users with access to the virtual machine's console.
The technical flaw stems from inadequate input validation and bounds checking within the VNC display driver's surface refresh mechanism. When processing display updates from guest operating systems, the function fails to properly validate the size or content of incoming data structures, leading to memory corruption in the heap allocation regions. This vulnerability is classified as CWE-121, heap-based buffer overflow, which occurs when a program writes data beyond the boundaries of heap-allocated memory blocks. The flaw is particularly dangerous because it operates within the context of a virtual machine's display subsystem, allowing guest users to manipulate host memory directly through the VNC interface.
The operational impact of this vulnerability extends beyond simple denial of service to potentially enabling arbitrary code execution on the host system. An attacker with guest access can craft malicious display update requests that overwrite adjacent heap memory, potentially corrupting critical data structures or even overwriting function pointers and return addresses. This creates a pathway for privilege escalation and remote code execution on the host machine running the vulnerable QEMU instance. The vulnerability affects virtualization environments where QEMU is used as the hypervisor platform, particularly impacting cloud computing deployments, virtual desktop infrastructures, and containerized environments that rely on QEMU for virtual machine management.
From an attack perspective, this vulnerability aligns with ATT&CK technique T1059.007 for command and control through virtualization software, and T1068 for exploit for privilege escalation. The attack surface is particularly concerning in multi-tenant cloud environments where guest users may not have direct access to the host system but can still influence the virtualization layer through display protocols. Mitigation strategies include immediate patching to QEMU version 2.4.0.1 or later, implementing network segmentation to restrict VNC access, disabling unnecessary VNC features, and applying memory protection mechanisms such as stack canaries and address space layout randomization. Organizations should also consider implementing monitoring for unusual VNC traffic patterns and conducting regular vulnerability assessments of their virtualization infrastructure to identify similar issues in other components of their virtualization stack.