CVE-2026-55491 BigBlueButton: Stored XSS in Screenshare Recording Playback via Unescaped Meeting Name
Attackers can inject scripts via meeting names that execute in other users' browsers during recording playback, potentially leading to session hijacking.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2026-55491?
CVE-2026-55491 is a medium-severity cross-site scripting vulnerability in bigbluebutton, published on 20 Aug 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.
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.
Weakness: CWE-79
Which versions are affected by CVE-2026-55491?
How do I fix CVE-2026-55491?
No fix has been published for CVE-2026-55491 yet. Limit exposure of the affected software until one is available.
Escape output for the context it lands in and set a strict Content Security Policy. Upgrading the affected component is the real fix. More about Cross-site scripting.
Is CVE-2026-55491 being exploited?
There is no known exploitation of CVE-2026-55491 in the wild and no public exploit code.
Sources
Also known as GHSA-57p5-c888-74f9.