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, 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:

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:

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