CVE-2015-8744 in QEMU
Summary
by MITRE
QEMU (aka Quick Emulator) built with a VMWARE VMXNET3 paravirtual NIC emulator support is vulnerable to crash issue. It occurs when a guest sends a Layer-2 packet smaller than 22 bytes. A privileged (CAP_SYS_RAWIO) guest user could use this flaw to crash the QEMU process instance resulting in DoS.
If you want to get best quality of vulnerability data, you may have to visit VulDB.
Analysis
by VulDB Data Team • 10/12/2022
The vulnerability identified as CVE-2015-8744 affects QEMU virtual machine emulators that incorporate VMware VMXNET3 paravirtual Network Interface Card emulator support. This flaw represents a critical denial-of-service condition that can be exploited by malicious actors within a virtualized environment. The issue specifically manifests when a guest operating system sends Layer-2 network packets that are smaller than 22 bytes in length, triggering an improper handling mechanism within the QEMU process that results in process termination.
The technical root cause of this vulnerability lies in the insufficient input validation within the VMXNET3 network interface emulator implementation. When QEMU receives packets below the 22-byte threshold, the network driver fails to properly handle the malformed data structure, leading to memory corruption or invalid pointer dereferences. This type of vulnerability falls under CWE-125, which describes out-of-bounds read conditions, and CWE-119, which encompasses weaknesses related to memory safety. The vulnerability exists at the boundary between the guest operating system and the hypervisor's network stack, where proper packet validation should occur but fails to do so.
From an operational perspective, this vulnerability presents a significant risk in virtualized environments where multiple users share the same host system. A guest user with CAP_SYS_RAWIO capabilities can leverage this flaw to crash the QEMU process, effectively causing denial-of-service for the entire virtual machine instance. The impact extends beyond individual VMs to potentially affect the stability of the entire host system, especially in cloud computing environments where multiple virtual machines may be running concurrently. This vulnerability aligns with ATT&CK technique T1499.001, which covers network denial-of-service attacks, and T1068, which addresses local privilege escalation through system-level capabilities.
The exploitation of this vulnerability requires minimal prerequisites as the guest user already possesses the necessary CAP_SYS_RAWIO capability, which typically grants access to raw I/O operations and network interface manipulation. This makes the attack vector particularly dangerous in multi-tenant environments where guest users may have elevated privileges for legitimate system administration tasks. The vulnerability demonstrates a classic case of insufficient data validation in virtualization components, where network packet handling routines fail to account for edge cases in packet size validation. Organizations implementing virtualized infrastructure should consider this vulnerability as part of their security posture assessment, particularly in environments where guest users might have access to system-level capabilities. The recommended mitigation strategies include applying the vendor-provided patches, implementing network segmentation to limit guest access to critical system resources, and monitoring for unusual network traffic patterns that might indicate exploitation attempts.