Vulnerability · Published Aug 20, 2026 · Assigned by GitHub_M

CVE-2026-55491BigBlueButton: Stored XSS in Screenshare Recording Playback via Unescaped Meeting Name

Medium 5.4

In plain English

A medium-severity cross-site scripting in bigbluebutton from bigbluebutton. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 22% of all known vulnerabilities).

Severity (CVSS 3.1)5.4Medium

Exploit odds (30 days)0.3%top 78.5% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

Vendor	Product	Versions
bigbluebutton	bigbluebutton	< 3.0.29

Weakness: CWE-79 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

References

https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-57p5-c888-74f9 x_refsource_CONFIRM
https://github.com/bigbluebutton/bigbluebutton/commit/a53f2b92022388bfa4109d3136d1f3a932404b1b x_refsource_MISC
https://github.com/bigbluebutton/bigbluebutton/releases/tag/v3.0.29 x_refsource_MISC