CVE-2017-18191 in OpenStack Nova
Summary
by MITRE
An issue was discovered in OpenStack Nova 15.x through 15.1.0 and 16.x through 16.0.4. By detaching and reattaching an encrypted volume, an attacker may access the underlying raw volume and corrupt the LUKS header, resulting in a denial of service attack on the compute host. (The same code error also results in data loss, but that is not a vulnerability because the user loses their own data.) All Nova setups supporting encrypted volumes are affected.
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Analysis
by VulDB Data Team • 11/10/2024
This vulnerability resides within the OpenStack Nova compute service and represents a critical security flaw that emerged in versions 15.x through 15.1.0 and 16.x through 16.0.4. The issue stems from improper handling of encrypted volume operations during the detach and reattach process, creating a pathway for unauthorized access to underlying raw storage devices. The vulnerability specifically affects systems that support encrypted volumes, making it a widespread concern across OpenStack deployments utilizing this functionality. According to CWE-284, this represents an improper access control weakness where the system fails to properly enforce access restrictions during volume operations, while the ATT&CK framework categorizes this under privilege escalation and defense evasion techniques. The flaw allows an attacker to exploit the volume management workflow to gain access to raw volume data that should remain protected within the LUKS encryption layer.
The technical implementation of this vulnerability occurs when an attacker performs a sequence of volume detachment and reattachment operations on encrypted volumes. During this process, the system fails to properly validate or restrict access permissions, allowing the attacker to bypass normal security controls that should prevent direct access to the underlying raw storage. The LUKS (Linux Unified Key Setup) header, which contains critical cryptographic metadata and encryption parameters, becomes vulnerable to modification or corruption. This corruption effectively renders the encrypted volume unusable and can result in complete data loss or denial of service conditions on the compute host where the volume is attached. The vulnerability exists at the interface between Nova's volume management and the underlying storage abstraction layer, where proper state management and access control enforcement are missing.
The operational impact of this vulnerability extends beyond simple service disruption to encompass potential data integrity compromise and system availability issues. When an attacker successfully corrupts the LUKS header through this method, they can cause immediate denial of service on the compute host, preventing legitimate users from accessing their encrypted volumes. The severity increases when considering that this attack can be executed by users who have legitimate access to the volume management interface, making it particularly dangerous in multi-tenant environments where privilege separation is critical. The vulnerability affects all Nova installations that support encrypted volumes, regardless of deployment configuration or security settings, making it a systemic risk rather than an isolated incident. Organizations may experience service outages, data recovery complications, and potential compliance violations when this vulnerability is exploited.
Mitigation strategies for this vulnerability should focus on immediate patch application to versions that address the underlying code flaw in Nova's volume handling mechanisms. System administrators must ensure that all OpenStack Nova components are updated to versions beyond the affected releases, typically 15.1.1 or 16.0.5, which contain the necessary fixes for proper volume access control during detach and reattach operations. Organizations should implement additional monitoring and logging around volume management operations to detect anomalous detachment and reattachment patterns that might indicate exploitation attempts. Network segmentation and access control policies should be strengthened to limit which users can perform volume operations, particularly those that involve encrypted volumes. The fix typically involves implementing proper state validation and access control checks during volume lifecycle operations, ensuring that LUKS headers and underlying raw volumes remain protected throughout the entire detachment and reattachment process. Regular security audits of volume management interfaces and proper incident response procedures should be established to detect and respond to potential exploitation attempts.