CVE-2026-27466 BigBlueButton: Exposed ClamAV port enables Denial of Service
Remote attackers can cause denial of service by exploiting exposed ClamAV ports resulting from flawed documentation instructions.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-27466?
CVE-2026-27466 is a high-severity vulnerability in bigbluebutton, published on 21 Feb 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
BigBlueButton is an open-source virtual classroom. In versions 3.0.21 and below, the official documentation for "Server Customization" on Support for ClamAV as presentation file scanner contains instructions that leave a BBB server vulnerable for Denial of Service. The flawed command exposes both ports (3310 and 7357) to the internet. A remote attacker can use this to send complex or large documents to clamd and waste server resources, or shutdown the clamd process. The clamd documentation explicitly warns about exposing this port. Enabling ufw (ubuntu firewall) during install does not help, because Docker routes container traffic through the nat table, which is not managed or restricted by ufw. Rules installed by ufw in the filter table have no effect on docker traffic. In addition, the provided example also mounts /var/bigbluebutton with write permissions into the container, which should not be required. Future vulnerabilities in clamd may allow attackers to manipulate files in that folder. Users are unaffected unless they have opted in to follow the extra instructions from BigBlueButton's documentation. This issue has been fixed in version 3.0.22.
Weakness: CWE-668
Which versions are affected by CVE-2026-27466?
It affects 1 product.
Products include Bigbluebutton Bigbluebutton.
How do I fix CVE-2026-27466?
No fix has been published for CVE-2026-27466 yet. Limit exposure of the affected software until one is available.
Is CVE-2026-27466 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-27466 exists.
Other vulnerabilities in bigbluebutton
Sources
Also known as GHSA-wmhx-qw2p-w6gc.