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CVE-2026-27466

Bigbluebutton vulnerability

7.2 HIGHPublic exploitEPSS 0.58%
  1. Published21 Feb 2026

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.

CVSS 3.1 breakdown

Attack vectorNetwork
Attack complexityLow
Privileges requiredNone
User interactionNone
ScopeChanged
ConfidentialityLow
IntegrityNone
AvailabilityLow
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:N/A:L

Affected products

Bigbluebutton< 3.0.22

Remediation

Fixed in
Bigbluebutton≥ 3.0.22

References

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Frequently asked

Is CVE-2026-27466 being actively exploited?

CVE-2026-27466 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.58%.

How severe is CVE-2026-27466?

CVE-2026-27466 has a CVSS 3.1 base score of 7.2, rated high. EPSS estimates a 0.58% probability of exploitation.

Which products are affected by CVE-2026-27466?

Affected products include Bigbluebutton.

How do I fix CVE-2026-27466?

Upgrade affected software to a fixed version, for example Bigbluebutton 3.0.22 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

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Data from the NVD, CISA KEV catalog and FIRST EPSS. CVSS 3.1 base score shown where available.