CVE-2007-5729 in QEMU
Summary
by MITRE
The NE2000 emulator in QEMU 0.8.2 allows local users to execute arbitrary code by writing Ethernet frames with a size larger than the MTU to the EN0_TCNT register, which triggers a heap-based buffer overflow in the slirp library, aka NE2000 "mtu" heap overflow. NOTE: some sources have used CVE-2007-1321 to refer to this issue as part of "NE2000 network driver and the socket code," but this is the correct identifier for the mtu overflow vulnerability.
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Analysis
by VulDB Data Team • 07/29/2019
The vulnerability described in CVE-2007-5729 represents a critical heap-based buffer overflow within the NE2000 network emulator component of QEMU version 0.8.2. This issue specifically affects the slirp library implementation that handles network packet processing, creating a dangerous condition where malicious input can lead to arbitrary code execution. The vulnerability manifests when local users manipulate Ethernet frames that exceed the Maximum Transmission Unit (MTU) size and write these oversized frames to the EN0_TCNT register, which serves as a critical control point for network transmission parameters within the emulated hardware.
The technical flaw stems from inadequate input validation within the network emulation layer, where the system fails to properly validate the size of Ethernet frames before processing them through the slirp networking stack. When an oversized frame is written to the EN0_TCNT register, the underlying buffer management code does not perform proper bounds checking, allowing data to overflow into adjacent memory regions. This heap-based overflow creates opportunities for memory corruption that can be exploited to overwrite critical program structures, function pointers, or return addresses. The vulnerability specifically maps to CWE-121, heap-based buffer overflow, and represents a classic example of insufficient boundary checking in network protocol handling code.
The operational impact of this vulnerability extends beyond simple privilege escalation as it enables local attackers to execute arbitrary code with the privileges of the QEMU process, potentially leading to complete system compromise. Since QEMU typically runs with elevated privileges when emulating virtual machines, successful exploitation could allow attackers to gain control over the host system, access sensitive data, or establish persistent backdoors. The vulnerability affects virtualization environments where QEMU is used for network emulation, making it particularly dangerous in cloud computing environments, development workstations, or any system where virtual machines are actively managed. Attackers can leverage this vulnerability to bypass traditional security controls that rely on virtual machine isolation.
Mitigation strategies for this vulnerability require immediate patching of QEMU to version 0.9.0 or later, which includes proper bounds checking for network frame sizes. System administrators should also implement network segmentation and access controls to limit local user privileges, reducing the attack surface for potential exploitation. The vulnerability aligns with ATT&CK technique T1059.007, which covers command and scripting interpreter usage, as exploitation typically involves crafting malicious network traffic to trigger the buffer overflow. Additionally, monitoring for unusual network traffic patterns and implementing runtime protections such as stack canaries or address space layout randomization can help detect or prevent exploitation attempts. Organizations should also consider disabling unnecessary network emulation features and regularly auditing virtualization configurations to minimize exposure to similar vulnerabilities in the broader QEMU codebase.