CVE-2026-33898 is a high-severity (CVSS 8.8) Improper Authentication vulnerability in github.com/lxc/incus/v6/cmd/incus. A fix is available for github.com/lxc/incus/v6/cmd/incus — see the affected versions and patch details below.
Local Incus UI web server vulnerable to nuthentication bypass
Exploitation Status
No confirmed exploitation observed yet
- A successful exploit gives an attacker total control of the affected component, not partial access.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-33898.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
github.com/lxc/incus/v6/cmd/incusReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.
Description
Incus is a system container and virtual machine manager. Prior to version 6.23.0, the web server spawned by incus webui incorrectly validates the authentication token such that an invalid value will be accepted. 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. Version 6.23.0 patches the issue.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/lxc/incus/v6/cmd/incus | all versions | 6.23.0go get github.com/lxc/incus/v6/cmd/incus@v6.23.0 |
Affected Products
incuslinuxcontainersDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/lxc/incus/v6/cmd/incus, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/lxc/incus/v6/cmd/incus to 6.23.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-33898 is resolved across your whole dependency graph.
Workarounds
Close the privilege gap rather than the entry point: audit which accounts, roles and service identities can reach the affected operation, drop the component to the least privilege it actually needs, and review file and directory permissions created by earlier installs — a default left in place is what makes this reachable.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
Important: This flaw in the `incus webui` component allows for privilege escalation and unauthorized access. The vulnerability arises from improper authentication token validation when tokens are passed in the URL, enabling a local attacker or a remote attacker (via user interaction) to gain access to Incus instances…
To mitigate this issue, avoid running the `incus webui` command if the web interface functionality is not required. The `incus webui` component spawns a local web server, and refraining from its use eliminates the attack vector. If `incus webui` must be used, ensure that only trusted users have access to the system where it is run and exercise caution with any remote interactions that might trick a local user into accessing the Incus UI web server.Source: Red Hat security advisory for CVE-2026-33898 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-33898 in your dependencies?
Find it across Go, including transitive dependencies.