CVE-2017-1000256 in libvirt
Summary
by MITRE
libvirt version 2.3.0 and later is vulnerable to a bad default configuration of "verify-peer=no" passed to QEMU by libvirt resulting in a failure to validate SSL/TLS certificates by default.
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Analysis
by VulDB Data Team • 12/02/2019
The vulnerability identified as CVE-2017-1000256 affects libvirt versions 2.3.0 and later, presenting a critical security flaw in the default configuration of SSL/TLS certificate validation. This issue stems from libvirt's default setting of "verify-peer=no" when establishing connections with QEMU hypervisors, creating a fundamental weakness in the security infrastructure that can be exploited by malicious actors. The flaw represents a failure in the principle of least privilege and secure by default configurations, where the system operates with inherently insecure defaults that require explicit user intervention to correct.
The technical implementation of this vulnerability occurs at the communication layer between libvirt and QEMU hypervisors, where SSL/TLS connections are established without proper certificate verification. When "verify-peer=no" is set, the system accepts any certificate presented by the remote peer without validating its authenticity, trust chain, or cryptographic integrity. This configuration allows for man-in-the-middle attacks where an attacker can intercept communications between libvirt and QEMU, potentially gaining unauthorized access to virtual machine management functions and compromising the entire virtualization environment. The vulnerability aligns with CWE-295 which specifically addresses improper certificate validation and CWE-310 which covers cryptographic issues related to secure communication protocols.
The operational impact of this vulnerability extends beyond simple network security concerns to encompass complete virtualization infrastructure compromise. An attacker who successfully exploits this vulnerability can gain unauthorized access to virtual machine management interfaces, potentially leading to privilege escalation, data exfiltration, and complete control over virtualized workloads. This risk is particularly severe in enterprise environments where libvirt is commonly used for managing large-scale virtual machine deployments, as it can enable attackers to move laterally within the virtualization infrastructure and potentially access sensitive data across multiple virtual machines. The vulnerability affects organizations using libvirt for KVM virtualization and could impact cloud computing environments that rely on secure hypervisor communication channels.
Mitigation strategies for CVE-2017-1000256 require immediate configuration updates to enforce proper SSL/TLS certificate validation. Organizations should modify libvirt configuration files to explicitly set "verify-peer=yes" and ensure that proper certificate authorities are configured for validation. System administrators must also implement certificate management policies that include regular certificate rotation and proper certificate distribution to all libvirt clients. The remediation process should include updating to libvirt versions that address this vulnerability and implementing network segmentation to limit exposure of virtualization management interfaces. This vulnerability demonstrates the importance of secure configuration management and aligns with ATT&CK technique T1071.004 for application layer protocol manipulation and T1566 for credential access through network infrastructure compromise. Organizations should also consider implementing network monitoring solutions to detect potential exploitation attempts and establish automated compliance checking to ensure that all libvirt instances maintain proper SSL/TLS configuration standards.