Pi-hole Cross-site Scripting

Pi-hole's Web interface provides a central location to manage a Pi-hole instance and review performance statistics. Prior to Pi-hole Web interface version 5.5.1, the function to add domains to blocklists or allowlists is vulnerable to a stored cross-site-scripting vulnerability. User input added as a wildcard domain to a blocklist or allowlist is unfiltered in the web interface. Since the payload is stored permanently as a wildcard domain, this is a persistent XSS vulnerability. A remote attacker can therefore attack administrative user accounts through client-side attacks. Pi-hole Web Interface version 5.5.1 contains a patch for this vulnerability. (2021-08-04, CVE-2021-32793)

Pi-hole is a Linux network-level advertisement and Internet tracker blocking application. The Stored XSS exists in the Pi-hole Admin portal, which can be exploited by the malicious actor with the network access to DNS server. See the referenced GitHub security advisory for patch details. (2021-04-15, CVE-2021-29448)

Pi-hole 5.0, 5.1, and 5.1.1 allows XSS via the Options header to the admin/ URI. A remote user is able to inject arbitrary web script or HTML due to incorrect sanitization of user-supplied data and achieve a Reflected Cross-Site Scripting attack against other users and steal the session cookie. (2021-02-18, CVE-2020-35592)

The DNS query log in Pi-hole before 5.2.2 is vulnerable to stored XSS. An attacker with the ability to directly or indirectly query DNS with a malicious hostname can cause arbitrary JavaScript to execute when the Pi-hole administrator visits the Query Log or Long-term data Query Log page. (2020-12-24, CVE-2020-35659)

Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.

The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:

https://server.com/confirmation?message=Transaction+Complete

what results in:

<span>Confirmation: Transaction Complete</span>

In that case the message can be modified to become a valid Javascript code, e.g.:

https://server.com/confirmation?message=<script>dangerous javascript code here</script>

and it will be executed locally by the user's browser with full access to the user's personal application/browser data:

<span>Confirmation: <script>dangerous javascript code here</script></span>