Medium severity · published Aug 20, 2026
CVE-2026-55491
BigBlueButton: Stored XSS in Screenshare Recording Playback via Unescaped Meeting Name
5.4
CVSS
0.3%
EPSS
No
On KEV
Description
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Attack vector
Network
Complexity
Low
Privileges
Low
User interaction
Required
Confidentiality
Low
Integrity
Low
Availability
None
Scope
Changed
Exploitation
Is it being used?
Exploit prediction (EPSS)0.3% · higher than 21% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
BI
bigbluebutton · bigbluebutton
< 3.0.29 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-55491
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-55491
github.com
https://github.com/bigbluebutton/bigbluebutton/commit/a53f2b92022388bfa4109d3136d1f3a932404b1b
github.com
https://github.com/bigbluebutton/bigbluebutton/releases/tag/v3.0.29
github.com
https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-57p5-c888-74f9
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