CVE-2026-48751 in Incus
Summary
by MITRE • 08/21/2026
Incus is a system container and virtual machine manager. Prior to version 7.2.0, instance snapshots ignore the `restricted.containers.lowlevel=block` setting; allowing for arbitrary command execution on the Incus server by abusing lowlevel hooks such as `raw.lxc` and `raw.qemu`. Version 7.2.0 patches the issue.
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Analysis
by VulDB Data Team • 08/21/2026
The vulnerability identified in Incus prior to version 7.2.0 represents a critical security flaw within the system container and virtual machine management platform, specifically concerning how instance snapshots interact with restricted configuration settings. Incus relies on a set of restrictions designed to limit what actions unprivileged users or compromised instances can perform against the host system. One such restriction is `restricted.containers.lowlevel=block`, which is intended to prevent containers from executing low-level hooks that could bypass standard isolation boundaries, such as those provided by raw LXC or QEMU configurations. These hooks are powerful mechanisms that allow direct interaction with underlying hypervisor features, and when improperly restricted, they can serve as a vector for privilege escalation or arbitrary command execution on the host server.
The core technical flaw lies in the snapshot creation process not respecting this specific restriction setting. When an administrator attempts to create a snapshot of a container or virtual machine that has `restricted.containers.lowlevel=block` enabled, the system fails to enforce the blockage during the serialization and storage phases associated with snapshots. This oversight allows attackers who have access to manage instances within these restricted environments to inject malicious configurations into the snapshot metadata. By abusing low-level hooks like `raw.lxc` or `raw.qemu`, an attacker can embed commands that are executed when the instance is restored from the snapshot, effectively bypassing the intended security controls and gaining arbitrary command execution capabilities on the Incus server host.
From a classification perspective, this vulnerability aligns with CWE-250, which denotes Execution with Unnecessary Privileges, as it allows an actor to perform actions beyond their authorized scope due to improper enforcement of access control mechanisms. Furthermore, in the context of the MITRE ATT&CK framework, this flaw facilitates techniques related to Defense Evasion and Privilege Escalation, specifically through the abuse of system-level hooks and configuration manipulation. The ability to execute arbitrary commands on the host server significantly expands the blast radius of a compromised container instance, potentially leading to full control over the underlying infrastructure if not contained properly by other security layers such as SELinux or AppArmor profiles that may be misconfigured alongside Incus restrictions.
The operational impact of this vulnerability is severe for any deployment relying on multi-tenant environments or untrusted workloads within Incus containers. An attacker with write access to instance configurations can leverage the snapshot mechanism to persist malicious payloads and execute them at will, regardless of the low-level restriction settings intended to mitigate such risks. This undermines the fundamental security model of containerization by allowing escape from user-space restrictions into kernel-host interactions via hypervisor hooks. The persistence aspect is particularly concerning because snapshots are often used for backup and recovery purposes, meaning that once a malicious snapshot is created, it may be restored on multiple hosts or over extended periods, providing long-term access to the compromised environment.
To mitigate this risk, organizations running Incus versions prior to 7.2.0 must upgrade immediately to version 7.2.0 or later, where the patch ensures that instance snapshots correctly respect and enforce the `restricted.containers.lowlevel=block` setting. In addition to upgrading, administrators should audit existing instances for any reliance on raw LXC or QEMU hooks in environments where low-level access is restricted. Implementing strict least-privilege principles for Incus user groups and regularly reviewing snapshot configurations can further reduce exposure. It is also advisable to monitor host system logs for unusual process executions originating from container contexts, as this may indicate exploitation attempts before the patch is applied.