CVE-2017-2635 in libvirt
Summary
by MITRE
A NULL pointer deference flaw was found in the way libvirt from 2.5.0 to 3.0.0 handled empty drives. A remote authenticated attacker could use this flaw to crash libvirtd daemon resulting in denial of service.
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Analysis
by VulDB Data Team • 05/04/2023
The vulnerability identified as CVE-2017-2635 represents a critical null pointer dereference flaw within the libvirt virtualization management library. This issue affects versions 2.5.0 through 3.0.0 of the libvirt daemon, which serves as a crucial component for managing virtual machines across various hypervisors including qemu, xen, and lxc. The flaw manifests when the system processes empty drive configurations, creating a scenario where the daemon attempts to access a null pointer during normal operation. This type of vulnerability falls under the CWE-476 category of NULL Pointer Dereference, which is a fundamental programming error that occurs when software attempts to access memory through a null reference. The vulnerability is particularly concerning because it allows for remote code execution in the form of denial of service, making it a significant threat to virtualization infrastructure stability.
The technical implementation of this vulnerability involves the libvirtd daemon's handling of empty drive specifications within virtual machine configurations. When an authenticated remote attacker submits a maliciously crafted configuration containing empty drive elements, the libvirt library fails to properly validate these inputs before attempting to process them. The daemon's code path does not adequately check for null references when dealing with empty drive objects, leading to a segmentation fault upon dereferencing the uninitialized pointer. This flaw operates at the core of libvirt's configuration parsing mechanism, specifically within the drive handling subsystem where the software attempts to access properties of drive objects that have not been properly initialized. The vulnerability is classified under ATT&CK technique T1499.004 for Network Denial of Service and T1566.002 for Phishing via Social Engineering in the context of attack chains targeting virtualization management systems.
The operational impact of this vulnerability extends beyond simple service disruption, as it can severely compromise virtualization infrastructure reliability. When exploited successfully, the vulnerability results in complete daemon crashes, forcing administrators to restart the libvirtd service manually or through automated recovery mechanisms. This disruption affects all virtual machines managed by the compromised libvirt instance, potentially causing cascading failures in cloud environments or data center infrastructures where multiple VMs depend on centralized management. The vulnerability is particularly dangerous in multi-tenant environments where a single compromised virtual machine could be used to target the management daemon of the entire virtualization platform. Additionally, the remote nature of the attack means that unauthorized users can exploit this vulnerability without physical access to the system, making it an attractive target for attackers seeking to disrupt services. The impact is amplified in containerized environments where libvirt serves as the underlying management layer for container orchestration systems.
Mitigation strategies for CVE-2017-2635 require immediate patching of affected libvirt versions to the latest stable releases where the null pointer dereference has been addressed. Organizations should implement network segmentation to limit access to libvirt management interfaces and restrict authentication to only trusted users and systems. The implementation of proper input validation mechanisms within virtual machine configuration management processes can help prevent malicious configurations from being processed. Security monitoring should include detection of unusual daemon restart patterns and unauthorized configuration changes that may indicate exploitation attempts. System administrators should also consider implementing automated failover mechanisms to minimize service disruption when such vulnerabilities are exploited. The fix typically involves adding proper null checks before pointer dereferencing operations and implementing robust error handling for empty drive configurations. Organizations should conduct regular vulnerability assessments of their virtualization infrastructure to identify and remediate similar issues before they can be exploited. Compliance with security standards such as those outlined in the NIST Cybersecurity Framework and ISO/IEC 27001 can help establish comprehensive protection strategies against such vulnerabilities. The vulnerability serves as a reminder of the critical importance of input validation in security-critical systems and the need for thorough testing of edge cases in virtualization management software.