CVE-2026-55491

BigBlueButton: Stored XSS in Screenshare Recording Playback via Unescaped Meeting Name

MEDIUM
5.4
CVSS Score
Published: August 20, 2026 at 09:35 PM UTC
Updated: October 26, 2026 at 10:10 AM UTC
1 product affected across 1 vendorBigbluebutton

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Severity
MEDIUM5.4
Exploit prediction
EPSS 0.3%
SSVC
No known exploit

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

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 3.0.29
Affected range stops below 3.0.29, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.4MEDIUMGitHub_M
Attack Vector
NETWORK
Complexity
LOW
Privileges
LOW
User Interaction
REQUIRED
Scope
CHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusDEFERRED
CWE
CWE-79

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