CVE-2026-63295 in LXD
Summary
by MITRE • 08/12/2026
An authorization bypass vulnerability in LXD allows an authenticated attacker to bypass project-level container isolation restrictions. When a project is configured with restrictions on container privileges (such as enforcing restricted.containers.privilege=isolated), LXD fails to enforce the requirement if an instance configuration omits the security.idmap.isolated key. An attacker can exploit this flaw by creating or updating an instance without explicitly setting security.idmap.isolated, bypassing the target project's security constraints.
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Analysis
by VulDB Data Team • 08/12/2026
This authorization bypass vulnerability in LXD represents a critical failure in container isolation mechanisms that undermines the security posture of containerized environments. The flaw exists within the project-level access control system where administrators configure security policies to enforce restricted container privileges through specific parameters such as restricted.containers.privilege=isolated. When these security measures are properly implemented, they should prevent unauthorized access and privilege escalation across container boundaries. However, the vulnerability stems from a missing validation check that occurs when instance configurations do not explicitly include the security.idmap.isolated key, creating an exploitable gap in the enforcement mechanism.
The technical implementation flaw lies in LXD's failure to consistently validate instance configurations against project-level security policies. When administrators establish projects with isolated container requirements, they expect these restrictions to be enforced regardless of how individual instances are configured. The absence of the security.idmap.isolated key in instance configuration should trigger a mandatory enforcement mechanism that either prevents creation or automatically applies the required isolation settings. This oversight creates a scenario where authenticated attackers can manipulate instance configurations to circumvent the intended security controls, effectively allowing them to gain unauthorized access to resources that should be restricted within the project boundaries.
The operational impact of this vulnerability extends beyond simple privilege escalation as it fundamentally compromises the security model of containerized environments. Attackers who can successfully exploit this flaw can bypass isolation restrictions that are designed to prevent container-to-container attacks, host system compromise, and lateral movement within container networks. This vulnerability directly relates to common attack patterns documented in the ATT&CK framework under privilege escalation and defense evasion techniques, where adversaries seek to manipulate system configurations to gain unauthorized access. The implications are particularly severe in multi-tenant environments where proper isolation is critical for security compliance and data protection.
Mitigation strategies should focus on implementing mandatory configuration requirements that ensure all instances within restricted projects automatically inherit the necessary isolation parameters. System administrators must enforce strict configuration policies that require explicit validation of instance settings against project-level restrictions, with automated enforcement mechanisms that prevent creation or modification of instances without proper isolation keys. The vulnerability demonstrates the importance of comprehensive input validation and consistent policy enforcement as outlined in CWE categories related to privilege management and access control failures. Organizations should implement regular security audits of container configurations and establish automated tools that monitor for missing security parameters, ensuring that all container deployments adhere to the defined project security requirements while maintaining operational efficiency through proper configuration management processes.