CVE-2026-46351: BigBlueButton: Insecure Randomness allows to guess user's conference session token and impersonate them

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-330

Description

BigBlueButton is an open-source virtual classroom. Prior to 3.0.21, bbb-web generated conference sessionToken values with insufficiently secure randomness in bbb-common-web/src/main/java/org/bigbluebutton/api/Util.java and bigbluebutton-web/grails-app/controllers/org/bigbluebutton/web/controllers/ApiController.groovy, allowing a session user to predict other users' conference session tokens and impersonate them. This issue is fixed in version 3.0.21.

Affected products

bigbluebutton: before 3.0.21

References

https://github.com/bigbluebutton/bigbluebutton/commit/8457886c248aeba5597ee8749267602d6d117e98
https://github.com/bigbluebutton/bigbluebutton/releases/tag/v3.0.21
https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-7959-pf2v-xc4h

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