CVE-2019-5604 in FreeBSD
Summary
by MITRE
In FreeBSD 12.0-STABLE before r350246, 12.0-RELEASE before 12.0-RELEASE-p8, 11.3-STABLE before r350247, 11.3-RELEASE before 11.3-RELEASE-p1, and 11.2-RELEASE before 11.2-RELEASE-p12, the emulated XHCI device included with the bhyve hypervisor did not properly validate data provided by the guest, allowing an out-of-bounds read. This provides a malicious guest the possibility to crash the system or access system memory.
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Analysis
by VulDB Data Team • 11/13/2023
The vulnerability identified as CVE-2019-5604 affects FreeBSD hypervisor implementations, specifically within the bhyve virtualization environment that emulates XHCI (eXtensible Host Controller Interface) USB controllers. This issue exists in multiple FreeBSD release versions including 11.2-RELEASE through 11.3-RELEASE and 12.0-RELEASE through 12.0-STABLE, representing a critical flaw in the virtualization stack that could compromise system integrity and security. The vulnerability stems from insufficient input validation mechanisms within the emulated XHCI device implementation, creating a pathway for malicious guest operating systems to exploit memory access patterns that should be strictly controlled.
The technical flaw manifests as an out-of-bounds read condition within the bhyve hypervisor's XHCI emulation layer where guest operating systems can provide malformed or malicious data to the emulated USB controller. This improper validation allows attackers to access memory locations beyond the intended boundaries of the emulated device, potentially enabling them to read arbitrary system memory contents or cause system crashes through controlled memory access violations. The vulnerability specifically impacts the virtualized USB controller emulation, where the hypervisor fails to properly sanitize data inputs from guest environments before processing them within the emulated hardware context.
The operational impact of this vulnerability extends beyond simple system instability, as it creates potential attack vectors for privilege escalation and information disclosure within virtualized environments. A malicious guest operating system could leverage this flaw to access sensitive kernel memory regions, potentially extracting confidential data or system credentials that would otherwise remain protected. The out-of-bounds read capability also provides attackers with the means to destabilize the hypervisor, leading to denial of service conditions that could affect all virtual machines running on the compromised host system. This vulnerability particularly impacts cloud environments and virtualized infrastructure where multiple tenants share the same physical hardware.
Mitigation strategies for CVE-2019-5604 primarily involve applying the relevant FreeBSD security patches that address the input validation gaps in the bhyve hypervisor's XHCI implementation. System administrators should prioritize updating their FreeBSD installations to versions that include fixes for this vulnerability, particularly focusing on the specific release branches mentioned in the advisory. Additionally, implementing network segmentation and access controls can help limit the potential impact of exploitation by restricting guest access to potentially malicious environments. The vulnerability aligns with CWE-129, which addresses improper validation of input boundaries, and may be categorized under ATT&CK technique T1059 for execution through hypervisor manipulation, highlighting the need for comprehensive virtualization security monitoring and hardening practices. Organizations should also consider implementing hypervisor-level monitoring to detect anomalous memory access patterns that could indicate exploitation attempts, as well as maintaining regular backup and recovery procedures to ensure business continuity in case of successful exploitation.