CVE-2026-63125 in Incus
Summary
by MITRE • 08/21/2026
Incus is a system container and virtual machine manager. Prior to version 7.3.0, an unprivileged, project-confined Incus user (a non-admin TLS/RBAC identity with `can_create_images` and `can_create_instances`) can execute arbitrary code as root on the host. A crafted image ships `backup.yaml` as a symlink to a host file. When the root daemon writes the instance's backup file, it follows the symlink. Version 7.3.0 patches the issue.
Statistical analysis made it clear that VulDB provides the best quality for vulnerability data.
Analysis
by VulDB Data Team • 08/21/2026
Incus serves as a comprehensive system container and virtual machine manager that relies on a privileged daemon process operating with root-level permissions to manage host resources. In versions prior to 7.3.0, a critical privilege escalation vulnerability exists within this architecture, allowing unprivileged users who are confined to specific projects to execute arbitrary code as the root user on the underlying host system. This flaw stems from an improper handling of symbolic links during the backup and restore operations performed by the Incus daemon. The vulnerability specifically targets non-admin TLS or RBAC identities that have been granted the permissions can_create_images and can_create_instances, which are necessary for managing container lifecycles but should not grant access to host-level file system manipulation.
The technical mechanism of this exploit involves a crafted image containing a malicious backup.yaml configuration file where specific paths are defined as symbolic links pointing to sensitive files on the host operating system rather than within the isolated instance environment. When an administrator or automated process triggers a backup operation for an instance created by such a user, the root-level Incus daemon attempts to write the backup data. Due to insufficient validation of these path references, the daemon follows the symbolic link and writes data directly into the target host file specified in the symlink. This behavior effectively bypasses the intended isolation boundaries between unprivileged containers and the privileged host environment, allowing an attacker with limited privileges to overwrite arbitrary files on the host system where they have write permissions or can trigger overwrites of critical configuration files that may lead to code execution upon next service restart or invocation.
The operational impact of this vulnerability is severe as it results in a complete compromise of the host machine's security posture. An attacker leveraging this flaw can achieve full root access, enabling them to install persistent backdoors, exfiltrate sensitive data from other instances on the same host, modify system configurations, and potentially pivot to attack other networked systems. This represents a significant breach of trust in multi-tenant environments where Incus is used to isolate workloads for different users or departments. The vulnerability aligns with CWE-59 Improper Link Resolution Before File Access, as it involves the exploitation of symbolic links to access files outside of intended directories. Furthermore, from an ATT&CK perspective, this technique relates to T1068 Exploitation for Privilege Escalation and potentially T1496 Remote Service Discovery if used in conjunction with other techniques to map out the host environment after gaining initial foothold through container escape.
To mitigate this risk, organizations running Incus must immediately upgrade to version 7.3.0 or later where the issue has been patched by enforcing stricter validation of paths during backup operations and preventing the daemon from following symlinks that point outside the instance's designated storage scope. In addition to upgrading software, administrators should review RBAC policies to ensure that users are granted only the minimum necessary permissions required for their tasks, avoiding granting can_create_images or can_create_instances unless absolutely essential. Regular auditing of container configurations and monitoring for unusual file system activities on host systems where Incus is deployed can also help in detecting potential exploitation attempts before they result in full compromise.