CVE-2023-33176
MediumCVSS 4.8Exploitation Probability (EPSS)
Low risk30th percentile - higher than 30% of all known CVEs
Summary
BigBlueButton, an open-source virtual classroom, has a Server-Side Request Forgery (SSRF) vulnerability in affected versions that allows users to supply a URL for downloading presentations without prior validation. An update to the `followRedirect` method has been made to validate all URLs used for presentation downloads.
Risk Assessment
This vulnerability could lead to unauthorized access to internal organizational resources, posing a serious threat to data security. The lack of proper safeguards may allow attackers to exploit this flaw to conduct attacks on network infrastructure.
Recommendation
It is recommended to upgrade to a patched version of BigBlueButton to implement the new URL validation properties. Administrators should also configure `presentationDownloadSupportedProtocols` and `presentationDownloadBlockedHosts` in the `bigbluebutton.properties` file.
Other vulnerabilities in BigBlueButton
See all- CVE-2026-55491Medium
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.
- CVE-2026-55489Medium
BigBlueButton is an open-source virtual classroom. Prior to 3.0.29, BigBlueButton presenters could submit a presentationId through /api/graphql that identified a presentation belonging to another meeting. akka-bbb-apps/src/main/scala/org/bigbluebutton/core/apps/presentationpod/RemovePresentationPubMsgHdlr.scala did not verify the presentation's meeting identifier before deletion, allowing a presenter who knew the identifier to delete another meeting's presentation and disrupt its availability. This issue is fixed in version 3.0.29.
- CVE-2026-46682High
BigBlueButton before version 3.0.23 allows authenticated moderators to inject SQL through the meetingId and userId values used by refreshBreakoutRoomsVisibleForUsers. The method interpolates these values into breakout room visibility queries, allowing arbitrary SQL execution against the application database. This issue is fixed in version 3.0.23.
- CVE-2026-46355High
BigBlueButton before version 3.0.23 exposed /bigbluebutton/api/handleJoinExistingUser, which was a routable controller action rather than a private helper. A requester able to supply an existingUserID for an active participant could reuse that participant's session and impersonate the participant in the same meeting. This issue is fixed in version 3.0.23.
- CVE-2026-46404Medium
BigBlueButton prior to version 3.0.23 improperly restricted access to local network addresses during presentation URL validation. The redirect following logic has been fixed to block local IP ranges.
- CVE-2026-46353High
In BigBlueButton prior to version 3.0.21, a vulnerability was found where checksum validation could be bypassed when a presentationUploadExternalUrl parameter was supplied to API request handling. This allows a user to send valid requests to some endpoints without a checksum.
- CVE-2026-46351High
BigBlueButton prior to version 3.0.21 generated conference session tokens with insufficiently secure randomness, allowing a session user to predict other users' tokens and impersonate them.
- CVE-2026-27737Medium
BigBlueButton prior to version 3.0.19 does not sanitize user input in public chat during recording playback. This allows a malicious actor to carry out an XSS attack that activates on anyone replaying the recording. The issue has been fixed in version 3.0.19.
Original NVD description (English source)
BigBlueButton is an open source virtual classroom designed to help teachers teach and learners learn. In affected versions are affected by a Server-Side Request Forgery (SSRF) vulnerability. In an `insertDocument` API request the user is able to supply a URL from which the presentation should be downloaded. This URL was being used without having been successfully validated first. An update to the `followRedirect` method in the `PresentationUrlDownloadService` has been made to validate all URLs to be used for presentation download. Two new properties `presentationDownloadSupportedProtocols` and `presentationDownloadBlockedHosts` have also been added to `bigbluebutton.properties` to allow administrators to define what protocols a URL must use and to explicitly define hosts that a presentation cannot be downloaded from. All URLs passed to `insertDocument` must conform to the requirements of the two previously mentioned properties. Additionally, these URLs must resolve to valid addresses, and these addresses must not be local or loopback addresses. There are no workarounds. Users are advised to upgrade to a patched version of BigBlueButton.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS