XSS in Bigbluebutton
CVE-2026-55491
BigBlueButton is an open-source virtual classroom. Prior to 3.0.29, BigBlueButton failed to escape meetingName in record-and-playback/screenshare/playback/index.html.erb when generating the screenshare playback format. A low-privileged user could store a crafted meeting name that embedded script content, and the script executed in another user's browser when that user replayed the recording. This issue is fixed in version 3.0.29.
Vulnerability class: XSS (Cross-Site Scripting)
CVSS v3 metric
CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.
Affected products
- Bigbluebutton — versions < 3.0.29
Weakness classification (CWE)
References
- security-advisories@github.com (x_refsource_CONFIRM)
- security-advisories@github.com (x_refsource_MISC)
- security-advisories@github.com (x_refsource_MISC)
Frequently asked questions
- What is CVE-2026-55491?
- CVE-2026-55491 is a medium-severity vulnerability in Bigbluebutton, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2026-08-20.
- How severe is CVE-2026-55491?
- Medium severity. CVSS v3 base score is 5.4 out of 10.