CVE-2017-15038 in QEMU
Summary
by MITRE
Race condition in the v9fs_xattrwalk function in hw/9pfs/9p.c in QEMU (aka Quick Emulator) allows local guest OS users to obtain sensitive information from host heap memory via vectors related to reading extended attributes.
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Analysis
by VulDB Data Team • 01/03/2023
The vulnerability identified as CVE-2017-15038 represents a critical race condition flaw within QEMU's 9p filesystem implementation that exposes sensitive host memory to unprivileged guest operating system users. This issue resides in the v9fs_xattrwalk function located in the hw/9pfs/9p.c source file, where improper synchronization mechanisms fail to prevent concurrent access patterns that could lead to information disclosure. The vulnerability specifically manifests when guest users attempt to read extended attributes from 9p filesystem exports, creating a window where host memory contents may be inadvertently exposed through memory access patterns that bypass normal security boundaries.
The technical exploitation of this race condition stems from inadequate locking mechanisms during attribute traversal operations within the 9p protocol implementation. When multiple threads or processes attempt concurrent access to extended attribute data structures, the lack of proper mutual exclusion allows for memory state corruption and information leakage. This vulnerability operates under CWE-362 which specifically addresses race conditions and concurrent access issues, where the flaw enables unauthorized information disclosure through improper synchronization. The 9p protocol implementation fails to maintain consistent state during attribute operations, creating opportunities for attackers to read adjacent memory regions that contain sensitive host data including potentially confidential information from other processes or system components.
The operational impact of CVE-2017-15038 extends beyond simple information disclosure, as it provides attackers with potential access to sensitive host memory contents that could include process credentials, cryptographic keys, or other confidential data. This vulnerability is particularly concerning in virtualized environments where guest operating systems are typically isolated from host resources, but the race condition allows for privilege escalation through memory access patterns that bypass normal isolation boundaries. The attack vector specifically targets local users within the guest OS who have access to 9p filesystem exports, making it a significant concern for cloud computing environments and virtualization platforms where multiple tenants share underlying infrastructure resources.
Mitigation strategies for this vulnerability require immediate patching of affected QEMU versions and implementation of proper synchronization mechanisms within the 9p filesystem implementation. System administrators should disable 9p filesystem exports when not required, particularly in multi-tenant environments where guest isolation is paramount. The fix typically involves implementing proper mutex locking or atomic operations around the attribute traversal functions to prevent concurrent access patterns that lead to memory leakage. Organizations should also consider implementing monitoring solutions to detect unusual memory access patterns that may indicate exploitation attempts. This vulnerability aligns with ATT&CK technique T1055 which covers process injection and memory manipulation techniques, as exploitation may involve memory access patterns that could be detected through behavioral monitoring systems. Additionally, the remediation should include thorough security testing of virtualized environments to ensure proper isolation boundaries remain intact after patching.