PYSEC-2026-1688

Nautobot's BANNER_* configuration can be used to inject arbitrary HTML content into Nautobot pages

### Impact A Nautobot user with admin privileges can modify the `BANNER_TOP`, `BANNER_BOTTOM`, and `BANNER_LOGIN` configuration settings via the `/admin/constance/config/` endpoint. Normally these settings are used to provide custom banner text at the top and bottom of all Nautobot web pages (or specifically on the login page in the case of `BANNER_LOGIN`) but it was reported that an admin user can make use of these settings to inject arbitrary HTML, potentially exposing Nautobot users to security issues such as cross-site scripting (stored XSS). ### Patches _Has the problem been patched? What versions should users upgrade to?_ Patches will be released as part of Nautobot 1.6.22 and 2.2.4. ### Workarounds _Is there a way for users to fix or remediate the vulnerability without upgrading?_ As [described in the Nautobot documentation](https://docs.nautobot.com/projects/core/en/stable/user-guide/administration/configuration/optional-settings/#administratively-configurable-settings), these settings are only configurable through the admin UI of Nautobot if they are *not* explicitly set to some non-empty value in the `nautobot_config.py` or equivalent Nautobot configuration file. Therefore, adding the following configuration to said file completely mitigates this vulnerability in both Nautobot 1.x and 2.x: ```python BANNER_LOGIN = " " BANNER_TOP = " " BANNER_BOTTOM = " " ``` or alternately (Nautobot 2.x only), if those variables are not defined explicitly in your configuration file, setting the following environment variables for the Nautobot user account serves the same purpose: ```shell NAUTOBOT_BANNER_LOGIN=" " NAUTOBOT_BANNER_TOP=" " NAUTOBOT_BANNER_BOTTOM=" " ``` Limiting all users who do not need elevated privileges to non-admin access (`is_superuser: False` and `is_staff: False`) is a partial mitigation as well. ### References - https://github.com/nautobot/nautobot/pull/5697 - https://github.com/nautobot/nautobot/pull/5698