CVE-2026-55622: 
Linux Debian vulnerability analysis and mitigation

CVE-2026-55622 is a project restriction bypass vulnerability in Incus (a system container and virtual machine manager) that allows an authenticated attacker to copy instances from projects they are not authorized to access. The flaw affects Incus versions prior to v7.2.0, and Debian 13 hosts lacking the fixed incus package version 6.0.4-2+deb13u8 are also affected. It was published on June 25, 2026, with a CVSS v3.1 base score of 7.7 (High) (Incus Advisory). A related vulnerability in LXD 5.0 (GHSA-qx75-2p3r-pwm5) was addressed in parallel via a separate pull request (LXD PR #18603).

The root cause is improper access control (CWE-284): when a POST request is made to /1.0/instances, the server authorizes the request against the target project but fails to verify whether the caller has view permission on the source project. Specifically, cmd/incusd/instances_post.go loads the source instance from req.Source.Project without checking whether the caller is authorized to view that source instance. An attacker who knows the name of a restricted project and an instance within it can craft a copy request specifying the restricted project as the source, effectively bypassing project-level access controls. A public proof-of-concept Python script was included in the security advisory (Incus Advisory).

Successful exploitation allows an authenticated but restricted attacker to copy container instances from projects they should not have access to, potentially exposing secrets, credentials, application data, or other sensitive information stored within those instances. Once copied to a project the attacker controls, the instance can be started, inspected, or moved to another server, enabling further data exfiltration or lateral movement within the infrastructure. The primary impact is high confidentiality loss with no direct integrity or availability impact (Incus Advisory).

A public proof-of-concept exploit script (Python) was published as part of the official security advisory, demonstrating how to copy a restricted instance using a valid but restricted client certificate. Exploitation requires network access to the Incus API endpoint (typically port 8443), a valid client certificate, and knowledge of the target project and instance names. No evidence of in-the-wild exploitation or threat actor attribution has been reported. The CVE status remains "Reserved" and no EPSS score or CISA KEV listing is currently available (Incus Advisory).

1. Reconnaissance: Identify a remotely accessible Incus server (default port 8443) running a vulnerable version (< v7.2.0). Obtain or enumerate the names of restricted projects and instances — this may be possible through social engineering, insider knowledge, or other information disclosure.
2. Obtain a restricted certificate: Acquire a valid client certificate that has been added to the Incus server but is restricted to specific projects (e.g., the default project only), excluding the target secret project.
3. Craft the copy request: Using the PoC script from the advisory, construct a POST request to /1.0/instances?project=<target-project> with a JSON body specifying source.type=copy, source.project=<restricted-project>, and source.source=<instance-name>.
4. Execute the exploit: Run the PoC: python3 poc.py --url https://<IP>:8443 --cert client.crt --key client.key --target-project default --source-project secrets --source-instance secret --name copy-secret --insecure. The server processes the copy without checking source project permissions.
5. Access the copied instance: After the copy completes, list instances in the target project (incus ls remote:) and start or inspect the copied instance to extract secrets, credentials, or other sensitive data (Incus Advisory).

• Network: Unexpected POST requests to /1.0/instances?project=<project> from client certificates that are restricted and should not have cross-project copy permissions; connections originating from unusual IP addresses to the Incus API port (8443).
• Logs: Incus daemon logs showing instance copy operations (source.type=copy) where the source project differs from the authenticated certificate's permitted projects; audit entries for instance creation in a project by a certificate not normally associated with that project.
• File System: Unexpected new container/VM instances appearing in projects, particularly with names matching instances from restricted projects; duplicated instance storage volumes in unexpected locations.
• Process: Incus daemon spawning copy/migration processes for instances across project boundaries without corresponding authorized user activity (Incus Advisory).

Upgrade Incus to version v7.2.0 or later, which enforces view permission checks on the source project before allowing instance or storage volume copies. Debian 13 users should update to the fixed package version 6.0.4-2+deb13u8 or later. For LXD 5.0 users, the fix is available in the stable-5.0 branch via PR #18603. As a temporary workaround, restrict network access to the Incus API endpoint (port 8443) to trusted clients only, and audit existing client certificate permissions to ensure restricted certificates cannot reach sensitive projects (Incus Advisory, LXD PR #18603).

The vulnerability was reported by security researcher antifob and remediated by Incus maintainer stgraber, who published the advisory and released Incus v7.2.0 on June 29, 2026. The Incus 7.2 release announcement was published on the maintainer's blog, and Tenable released multiple Nessus plugins (323053, 323320, 323596) to detect the vulnerability shortly after disclosure. Linux-compatible.org covered the Debian package updates addressing this and related vulnerabilities (Incus Advisory, Incus 7.2 Blog).