CVE-2026-27737 BigBlueButton has Stored XSS in bbb-playback replay
Attackers can inject malicious scripts into public chat messages that execute when users replay recordings, potentially compromising viewer accounts.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2026-27737?
CVE-2026-27737 is a medium-severity cross-site scripting vulnerability in bigbluebutton bbb-playback, published on 18 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
BigBlueButton is an open-source virtual classroom. In versions prior to 3.0.19, the recording playback (presentation format) was not sanitizing user's input in public chat. This allowed for a malicious actor to craft and carry out a targeted XSS attack, activated on anyone replaying the recording. This issue has been fixed 3.0.19.
Weakness: CWE-79
Which versions are affected by CVE-2026-27737?
How do I fix CVE-2026-27737?
No fix has been published for CVE-2026-27737 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-2026-27737 being exploited?
There is no known exploitation of CVE-2026-27737 in the wild and no public exploit code.
Sources
Also known as GHSA-8vv7-vj94-q2pv.