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

Quick assessment

Affected
bigbluebutton bigbluebutton
Exploitation
Public or AI PoC available; prioritize validation
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

BigBlueButton 是一款开源的虚拟教室应用。在版本 3.0.23 之前，BigBlueButton 通过 bigbluebutton-web/grails-app/controllers/org/bigbluebutton/web/controllers/ApiController.groovy 暴露了 /bigbluebutton/api/handleJoinExistingUser 接口。攻击者若能提供某个活跃参与者的 existingUserID，便可复用该参与者的会话，在同一会议中冒充该参与者。这

CVSS 7.1 · High EPSS 0.21% · P11

Possible ATT&CK Techniques 1 AI

T1078 · Valid Accounts

Affected Version Matrix 1

VendorProduct Version RangeStatus
bigbluebutton bigbluebutton < 3.0.23 affected
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I. Basic Information for CVE-2026-46355

Vulnerability Information
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Vulnerability Title
BigBlueButton: Unauthenticated Session Hijack via Exposed /bigbluebutton/api/handleJoinExistingUser
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:H/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
认证机制不恰当
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
bigbluebutton bigbluebutton < 3.0.23 -

II. Public POCs for CVE-2026-46355

# POC Description Source Link Shenlong Link
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Qwen3.6-35B-A3B · 8670 chars
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III. Intelligence Information for CVE-2026-46355

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Patches & Fixes for CVE-2026-46355 (1)

Vendor Advisories for CVE-2026-46355 (1)

Vendor Pages for CVE-2026-46355 (1)

Same Patch Batch · bigbluebutton · 2026-08-20 · 4 CVEs total

CVE-2026-46682 8.5 HIGH BigBlueButton: Blind SQL Injection AUTH (Moderator)
CVE-2026-55491 5.4 MEDIUM BigBlueButton: Stored XSS in Screenshare Recording Playback via Unescaped Meeting Name
CVE-2026-55489 4.9 MEDIUM BigBlueButton: IDOR on BBB through /api/graphql via POST parameter "presentationId" leads

IV. Related Vulnerabilities

Same product: bigbluebutton
Same vendor: bigbluebutton
Same weakness: CWE-287

V. Comments for CVE-2026-46355

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