CVE-2026-33898

The web server spawned by incus webui incorrectly validates the authentication token such that an invalid value will be accepted.

Details

incus webui runs a local web server on a random localhost port. For authentication, it provides the user with a URL containing an authentication token. When accessed with that token, Incus creates a cookie persisting that token without needing to include it in subsequent HTTP requests.

While the Incus client correctly validates the value of the cookie, it does not correctly validate the token when passed int the URL.
This allows for an attacker able to locate and talk to the temporary web server on localhost to have as much access to Incus as the user who ran incus webui.

This can lead to privilege escalation by another local user or an access to the user's Incus instances and possibly system resources by a remote attack able to trick the local user into interacting with the Incus UI web server.

Credit

This issue was discovered and reported by the team at 7asecurity

The application does not adequately verify the identity of a user, device, or process before granting access. Typical impact: unauthorized access to functions or data reserved for authenticated parties.

CVE-2026-33898 has a CVSS score of 8.8 (High). The vector is network-reachable, no privileges required, and user interaction required. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (6.23.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-33898? CVE-2026-33898 is a high-severity improper authentication vulnerability in github.com/lxc/incus/v6/cmd/incus (go), affecting versions < 6.23.0. It is fixed in 6.23.0. The application does not adequately verify the identity of a user, device, or process before granting access.
2. How severe is CVE-2026-33898? CVE-2026-33898 has a CVSS score of 8.8 (High). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of github.com/lxc/incus/v6/cmd/incus are affected by CVE-2026-33898? github.com/lxc/incus/v6/cmd/incus (go) versions < 6.23.0 is affected.
4. Is there a fix for CVE-2026-33898? Yes. CVE-2026-33898 is fixed in 6.23.0. Upgrade to this version or later.
5. Is CVE-2026-33898 exploitable, and should I be worried? Whether CVE-2026-33898 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-33898 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-33898? Upgrade github.com/lxc/incus/v6/cmd/incus to 6.23.0 or later.