CVE-2016-7116 in QEMU
Summary
by MITRE
Directory traversal vulnerability in hw/9pfs/9p.c in QEMU (aka Quick Emulator) allows local guest OS administrators to access host files outside the export path via a .. (dot dot) in an unspecified string.
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Analysis
by VulDB Data Team • 10/05/2022
The CVE-2016-7116 vulnerability represents a critical directory traversal flaw within QEMU's 9p filesystem implementation that enables local guest operating system administrators to escape the designated export path and access arbitrary host files. This vulnerability exists in the hw/9pfs/9p.c component of QEMU, which implements the 9P protocol for filesystem sharing between guest and host systems. The flaw specifically manifests when processing unspecified string inputs containing .. (dot dot) sequences that should normally be restricted to prevent path traversal attacks.
The technical implementation of this vulnerability stems from insufficient input validation and path resolution logic within the 9P filesystem server. When a guest administrator submits a request containing directory traversal sequences, the QEMU implementation fails to properly sanitize these inputs before resolving file paths on the host system. This allows malicious guest users with administrative privileges to navigate beyond the intended export boundaries and access files that should remain restricted to the host environment. The vulnerability operates at the filesystem abstraction layer where guest requests are translated into host filesystem operations, creating a direct pathway for unauthorized access.
From an operational impact perspective, this vulnerability presents a severe security risk for virtualized environments where guest operating systems are granted administrative privileges. Local guest administrators can exploit this flaw to read sensitive host files including configuration data, authentication credentials, system logs, and other potentially confidential information. The attack vector is particularly dangerous because it requires only local administrative access within the guest system, eliminating the need for network-based exploitation or additional privilege escalation. This makes it especially concerning in multi-tenant virtualized environments where guest isolation is paramount for security.
The vulnerability aligns with CWE-22 Directory Traversal and represents a classic case of inadequate input validation in server-side applications. From an attacker's perspective, this flaw maps to techniques described in the MITRE ATT&CK framework under T1059 Command and Scripting Interpreter and T1078 Valid Accounts, as it allows privilege escalation through local administrative access. The exploitability of this vulnerability is enhanced by the fact that QEMU's 9P implementation is commonly used in virtualization environments, making it a widespread target. Organizations using QEMU for virtualization should consider this vulnerability as part of their baseline security assessment, particularly in environments where guest isolation is critical. The recommended mitigation involves upgrading to patched versions of QEMU where proper input validation and path sanitization have been implemented to prevent directory traversal sequences from escaping the designated export paths.