Vulnerability · Published Aug 20, 2026 · Assigned by GitHub_M

CVE-2026-46355BigBlueButton: Unauthenticated Session Hijack via Exposed /bigbluebutton/api/handleJoinExistingUser

High 7.1

In plain English

A high-severity improper authentication in bigbluebutton from bigbluebutton. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.4% (higher than 31% of all known vulnerabilities).

Severity (CVSS 3.1)7.1High

Exploit odds (30 days)0.4%top 68.9% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

BigBlueButton is an open-source virtual classroom. Prior to 3.0.23, BigBlueButton exposed /bigbluebutton/api/handleJoinExistingUser through bigbluebutton-web/grails-app/controllers/org/bigbluebutton/web/controllers/ApiController.groovy. 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 because handleJoinExistingUser was a routable controller action rather than a private helper. This issue is fixed in version 3.0.23.

Affected products (as reported)

Vendor	Product	Versions
bigbluebutton	bigbluebutton	< 3.0.23

Weakness: CWE-287 · Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N

References

https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-38fw-2gq7-ccgr x_refsource_CONFIRM
https://github.com/bigbluebutton/bigbluebutton/commit/972b04e474e195cbd708b5b3f0485fe528a1a85b x_refsource_MISC
https://github.com/bigbluebutton/bigbluebutton/releases/tag/v3.0.23 x_refsource_MISC