What is CVE-2026-27736?

CVE-2026-27736 is a medium-severity vulnerability in Bigbluebutton, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2026-02-25.

How severe is CVE-2026-27736?

Medium severity. CVSS v3 base score is 6.1 out of 10.

Open Redirect in Bigbluebutton

CVE-2026-27736

BigBlueButton is an open-source virtual classroom. In versions on the 3.x branch prior to 3.0.20, the string received with errorRedirectUrl lacks validation, using it directly in the respondWithRedirect function leads to an Open Redirect vulnerability. BigBlueButton 3.0.20 patches the issue. No known workarounds are available.

Vulnerability class: Open Redirect

Published 2026-02-25 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.003 (15.9th percentile), scored 2026-10-01.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 16th percentile — 15.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.001 · newest: 0.003 · change: +0.001

Affected products

Bigbluebutton — versions >= 3.0.0, < 3.0.20

Weakness classification (CWE)

CWE-601 — URL Redirection to Untrusted Site (Open Redirect)

References

github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-65cv-rg9f-qqrx (Patch, Vendor Advisory)
github.com/bigbluebutton/bigbluebutton/commit/691f92f3af0d6b796b91cb96897706866… (Patch)

Frequently asked questions

What is CVE-2026-27736?: CVE-2026-27736 is a medium-severity vulnerability in Bigbluebutton, classified under URL Redirection to Untrusted Site (Open Redirect). CVSS score: 6.1/10. Published 2026-02-25.
How severe is CVE-2026-27736?: Medium severity. CVSS v3 base score is 6.1 out of 10.