CVE-2026-46353: BigBlueButton API checksum bypass via presentationUploadExternalUrl

Severity: high (CVSS 8.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-07-16 · updated 2026-07-17
Weakness: CWE-284

Description

BigBlueButton is an open-source virtual classroom. Prior to 3.0.21, bbb-web checksum validation could be bypassed when a presentationUploadExternalUrl parameter was supplied to API request handling in CreateMeeting.java and ValidationService.java, allowing a user to send valid requests to some endpoints without a checksum. This issue is fixed in version 3.0.21.

Affected products

bigbluebutton: before 3.0.21

References

https://github.com/bigbluebutton/bigbluebutton/commit/36fd1b407488a0c56ce620b91184d5a8aea68b3d
https://github.com/bigbluebutton/bigbluebutton/releases/tag/v3.0.21
https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-43hc-5g2m-cqff

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