[ASA-202111-5] grafana: cross-site scripting

[Jonas Witschel]

Arch Linux Security Advisory ASA-202111-5
=========================================

Severity: Medium
Date    : 2021-11-05
CVE-ID  : CVE-2021-41174
Package : grafana
Type    : cross-site scripting
Remote  : Yes
Link    : https://security.archlinux.org/AVG-2517

Summary
=======

The package grafana before version 8.2.3-1 is vulnerable to cross-site
scripting.

Resolution
==========

Upgrade to 8.2.3-1.

# pacman -Syu "grafana>=8.2.3-1"

The problem has been fixed upstream in version 8.2.3.

Workaround
==========

To mitigate the issue, a reverse proxy or similar can be used to block
access to block the literal string "{{" in the path.

Description
===========

A security issue has been found in Grafana before version 8.2.3. If an
attacker is able to convince a victim to visit a URL referencing a
vulnerable page, arbitrary JavaScript content may be executed within
the context of the victim's browser.

The user visiting the malicious link must be unauthenticated and the
link must be for a page that contains the login button in the menu bar.

There are two ways an unauthenticated user can open a page in Grafana
that contains the login button:
- Anonymous authentication is enabled. This means all pages in Grafana
would be open for the attack.
- The link is to an unauthenticated page. The following pages are
vulnerable:
  - /dashboard-solo/snapshot/*
  - /dashboard/snapshot/*
  - /invite/:code

The url has to be crafted to exploit AngularJS rendering and contain
the interpolation binding for AngularJS expressions. AngularJS uses
double curly braces for interpolation binding: {{ }}

An example of an expression would be:
"{{constructor.constructor(‘alert(1)’)()}}". This can be included in
the link URL like this:

https://play.grafana.org/dashboard/snapshot/%7B%7Bconstructor.construct
or('alert(1)')()%7D%7D?orgId=1

When the user follows the link and the page renders, the login button
will contain the original link with a query parameter to force a
redirect to the login page. The URL is not validated and the AngularJS
rendering engine will execute the JavaScript expression contained in
the URL.

Impact
======

A remote attacker could execute arbitrary JavaScript code by tricking
an unauthenticated victim into opening a crafted URL.

References
==========

https://github.com/grafana/grafana/security/advisories/GHSA-3j9m-hcv9-rpj8
https://github.com/grafana/grafana/commit/34eda6123d9b21c2c0b2d0c0e6f2fb38e6cf60d5
https://github.com/grafana/grafana/commit/a3dc30546fce2e437d858c140f1ff307a04365d6
https://github.com/grafana/grafana/commit/8081dc9ee913a1bf4b98f99e78661db88a6dc1ef
https://github.com/grafana/grafana/commit/1c7ce348ce4363c55992ed5772f96981d1a86f7e
https://security.archlinux.org/CVE-2021-41174
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