high CVSS 7.2

CVE-2026-27466·Docker vulnerability

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.

Severity
high
Software
Docker
Fixed in
3.0.22
Published
2026-02-21

Affected versions

Until: 3.0.22

Fixed in: 3.0.22

How to fix this CVE

Upgrade Docker to version 3.0.22 or later to address this vulnerability. If you have followed BigBlueButton's ClamAV integration documentation, immediately review your Docker networking configuration to restrict access to ports 3310 and 7357, and remove unnecessary write permissions from mounted volumes. Apply firewall rules at the host level to prevent external access to ClamAV container ports.

sudo dnf upgrade docker-ce

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check Docker version with 'docker --version' and compare against 3.0.22
  2. Step 2: List running containers with 'docker ps' and inspect ClamAV containers using 'docker port <container_id>' to check if ports 3310 or 7357 are exposed to 0.0.0.0
  3. Step 3: Review Docker container configurations with 'docker inspect <container_id>' and verify volume mounts do not include /var/bigbluebutton with write permissions
  4. Step 4: Confirm the fix by verifying upgraded Docker version and re-inspecting container port bindings to ensure ClamAV ports are not publicly accessible

FAQ

What is CVE-2026-27466?

This vulnerability affects BigBlueButton servers running version 3.0.21 and earlier that have implemented ClamAV antivirus scanning following official documentation. The flawed configuration exposes ClamAV daemon ports to the internet, allowing remote attackers to trigger denial-of-service conditions by sending malicious or oversized documents to exhaust server resources.

Is CVE-2026-27466 being actively exploited?

No, there is no evidence of active exploitation or publicly available exploits for this vulnerability at this time.

What versions of Docker are affected by CVE-2026-27466?

BigBlueButton versions up to and including 3.0.21 are vulnerable. The vulnerability is patched in version 3.0.22 and later.

How do I check if my server is vulnerable to CVE-2026-27466?

Run 'docker ps' to list containers, then execute 'docker port <clamd_container_id>' to check if ports 3310 or 7357 are bound to 0.0.0.0. If they are, your system is vulnerable. Additionally, check your docker-compose or container run commands for mounted volumes with /var/bigbluebutton write access.

Does Defensia detect CVE-2026-27466?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Docker is installed on a monitored server, CVE-2026-27466 will appear in your dashboard with remediation steps.

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References

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