CVE-2026-33898: CWE-287: Improper Authentication in lxc incus
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.
AI Analysis
Technical Summary
Incus versions before 6.23.0 have a vulnerability in the `incus webui` local web server where authentication tokens passed via URL are not properly validated. Although the Incus client validates cookie tokens correctly, the initial token in the URL is accepted even if invalid. Since `incus webui` runs a local web server on a random localhost port and uses a token-based URL for authentication, an attacker able to access this local server can gain the same privileges as the legitimate user. This can result in privilege escalation or unauthorized access to Incus instances and potentially system resources. The vulnerability is addressed in version 6.23.0.
Potential Impact
An attacker with local access to the machine can exploit this vulnerability to gain the same access rights as the user running `incus webui`, potentially escalating privileges. Additionally, a remote attacker might exploit this by tricking a local user into interacting with the vulnerable Incus UI web server, leading to unauthorized access to container and VM management functions and possibly broader system resources. The CVSS score of 8.8 reflects high impact on confidentiality, integrity, and availability.
Mitigation Recommendations
Version 6.23.0 of Incus includes an official fix for this vulnerability. Users should upgrade to version 6.23.0 or later to remediate this issue. Until upgraded, restrict access to the local web server spawned by `incus webui` to trusted users only and avoid interacting with untrusted URLs that may contain authentication tokens.
CVE-2026-33898: CWE-287: Improper Authentication in lxc incus
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.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
Incus versions before 6.23.0 have a vulnerability in the `incus webui` local web server where authentication tokens passed via URL are not properly validated. Although the Incus client validates cookie tokens correctly, the initial token in the URL is accepted even if invalid. Since `incus webui` runs a local web server on a random localhost port and uses a token-based URL for authentication, an attacker able to access this local server can gain the same privileges as the legitimate user. This can result in privilege escalation or unauthorized access to Incus instances and potentially system resources. The vulnerability is addressed in version 6.23.0.
Potential Impact
An attacker with local access to the machine can exploit this vulnerability to gain the same access rights as the user running `incus webui`, potentially escalating privileges. Additionally, a remote attacker might exploit this by tricking a local user into interacting with the vulnerable Incus UI web server, leading to unauthorized access to container and VM management functions and possibly broader system resources. The CVSS score of 8.8 reflects high impact on confidentiality, integrity, and availability.
Mitigation Recommendations
Version 6.23.0 of Incus includes an official fix for this vulnerability. Users should upgrade to version 6.23.0 or later to remediate this issue. Until upgraded, restrict access to the local web server spawned by `incus webui` to trusted users only and avoid interacting with untrusted URLs that may contain authentication tokens.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-03-24T15:41:47.490Z
- Cvss Version
- 3.1
- State
- PUBLISHED
Threat ID: 69c5c16a3c064ed76fe46d11
Added to database: 3/26/2026, 11:29:46 PM
Last enriched: 4/3/2026, 1:11:36 PM
Last updated: 5/11/2026, 5:21:11 AM
Views: 88
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