CVE-2017-13672 in QEMU
Summary
by MITRE
QEMU (aka Quick Emulator), when built with the VGA display emulator support, allows local guest OS privileged users to cause a denial of service (out-of-bounds read and QEMU process crash) via vectors involving display update.
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Analysis
by VulDB Data Team • 12/27/2022
CVE-2017-13672 represents a critical vulnerability in QEMU's VGA display emulator component that enables local privilege escalation within guest operating systems to execute denial of service attacks. This vulnerability specifically affects QEMU installations that include VGA display emulator support, making it particularly dangerous in virtualized environments where multiple guest operating systems share the same host resources. The flaw manifests through improper handling of display update operations, creating conditions where malicious code within a guest OS can trigger out-of-bounds memory reads that ultimately crash the QEMU process responsible for managing the virtual machine's graphics output.
The technical nature of this vulnerability stems from inadequate bounds checking within the VGA display emulator's update mechanisms. When a guest operating system attempts to perform display operations, particularly those involving graphics rendering or screen updates, the emulator fails to properly validate memory access parameters. This allows a privileged guest user to craft specific display update commands that reference memory locations outside the intended buffer boundaries, resulting in memory corruption and subsequent process termination. The vulnerability aligns with CWE-125, which describes out-of-bounds read conditions, and CWE-248, which covers improper exception handling leading to crashes.
From an operational perspective, this vulnerability poses significant risks to virtualization environments where guest OS users may have elevated privileges or where privilege escalation has occurred through other means. The impact extends beyond simple service disruption as a compromised QEMU process can lead to complete virtual machine crashes, potentially affecting multiple users in shared hosting environments or causing service interruptions in cloud computing platforms. Attackers can leverage this vulnerability to repeatedly crash virtual machines, creating persistent denial of service conditions that may be difficult to detect and remediate.
The attack surface for this vulnerability is particularly concerning given that many virtualization platforms rely heavily on QEMU for their core functionality, including cloud providers, development environments, and enterprise virtualization solutions. The local privilege requirement means that an attacker must already have access to a guest operating system with sufficient privileges to execute malicious code, but this access is often achievable through various attack vectors including social engineering, exploitation of other vulnerabilities, or legitimate administrative access. Organizations should consider this vulnerability in the context of ATT&CK technique T1059, which covers command and script injection, as attackers may use display update commands as part of broader exploitation strategies.
Mitigation strategies should focus on immediate patching of QEMU installations to address the bounds checking deficiencies in the VGA display emulator. System administrators should prioritize updating QEMU to versions that include proper memory validation for display operations, typically those released after the vulnerability disclosure. Additionally, implementing network segmentation and access controls can limit the potential impact by reducing the attack surface available to privileged guest users. Monitoring for unusual display update patterns or process crashes within virtualized environments can help detect exploitation attempts, while maintaining regular security audits of virtualization infrastructure can identify other potential vulnerabilities that may be exploited in conjunction with this flaw.