CVE-2020-15859 in QEMU
Summary
by MITRE
QEMU 4.2.0 has a use-after-free in hw/net/e1000e_core.c because a guest OS user can trigger an e1000e packet with the data's address set to the e1000e's MMIO address.
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Analysis
by VulDB Data Team • 11/23/2025
The vulnerability identified as CVE-2020-15859 represents a critical use-after-free flaw in QEMU version 4.2.0 affecting the e1000e network driver implementation. This issue resides within the hardware network interface emulation component located at hw/net/e1000e_core.c, where improper memory management allows for potential arbitrary code execution. The vulnerability specifically manifests when a guest operating system user crafts a malicious packet with data address set to the e1000e's Memory-Mapped I/O address space, creating a scenario where freed memory locations are accessed after deallocation.
The technical root cause of this vulnerability aligns with CWE-416, which describes use-after-free conditions where memory is accessed after it has been freed by the program. In the context of QEMU virtualization, this occurs when the e1000e network adapter emulation does not properly validate or handle packet data structures that reference MMIO addresses. When a guest OS sends a specially crafted packet with a data pointer pointing to the e1000e MMIO region, the emulator fails to properly manage the memory lifecycle, leading to a situation where freed memory blocks are subsequently accessed, potentially allowing for memory corruption and control flow hijacking.
From an operational perspective, this vulnerability presents a significant risk in virtualized environments where guest operating systems maintain network access. The attack vector requires a malicious guest user to craft and transmit specific network packets, but the impact extends beyond the individual guest to potentially affect the host system and other virtual machines running on the same hypervisor. This represents a privilege escalation scenario where a guest user could leverage this flaw to execute arbitrary code with the privileges of the QEMU process, potentially leading to full system compromise. The vulnerability's exploitation aligns with ATT&CK technique T1059.007 for command and script execution, and T1068 for local privilege escalation through process injection mechanisms.
The security implications of CVE-2020-15859 extend beyond immediate exploitation potential to encompass broader virtualization security concerns. Virtual machine escape attacks leveraging such use-after-free conditions can undermine the fundamental security isolation guarantees that virtualization platforms are designed to provide. Organizations running QEMU-based virtualization environments should consider this vulnerability as a critical threat requiring immediate remediation, particularly in multi-tenant cloud deployments or environments where guest isolation is paramount. The flaw demonstrates the importance of rigorous memory management practices in virtualization software and highlights the need for comprehensive input validation in emulated hardware components. Mitigation strategies should include immediate patching to QEMU version 4.2.1 or later, implementation of network traffic monitoring to detect suspicious packet patterns, and consideration of additional virtualization security controls such as memory access restrictions and process isolation measures to limit potential exploitation impact.