CVE-2021-43794 Anonymous user cache poisoning via development-mode header in Discourse
Attackers can poison the cache for anonymous users in development mode, causing them to receive JSON instead of HTML, leading to partial denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2021-43794?
CVE-2021-43794 is a medium-severity denial of service vulnerability in Discourse Discourse, published on 1 Dec 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
Discourse is an open source discussion platform. In affected versions an attacker can poison the cache for anonymous (i.e. not logged in) users, such that the users are shown a JSON blob instead of the HTML page. This can lead to a partial denial-of-service. This issue is patched in the latest stable, beta and tests-passed versions of Discourse.
Weakness: CWE-610
Which versions are affected by CVE-2021-43794?
1 open source package ship an affected version, including discourse. It affects 1 product.
| Package | Affected | Fixed in |
|---|---|---|
discourse Bitnami | All versions | 2.7.11 |
Products include Discourse Discourse.
How do I fix CVE-2021-43794?
Upgrade discourse to 2.7.11 or later.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2021-43794 being exploited?
There is no known exploitation of CVE-2021-43794 in the wild and no public exploit code.
Other vulnerabilities in Discourse Discourse
- CVE-2021-41163 RCE via malicious SNS subscription payload
- CVE-2022-36066 Discourse vulnerable to RCE via admins uploading maliciously zipped file
- CVE-2022-39356 Discourse user account takeover via email and invite link
- CVE-2023-22468 Discourse vulnerable to Cross-site Scripting in local oneboxes
- CVE-2026-27934 Discourse leaks private topic title and post excerpt via user action API endpoint
Sources
Also known as BIT-discourse-2021-43794, GHSA-249g-pc77-65hp.