EUVD-2026-44996Severity by source
AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Requires an existing valid session so PR:L; network-reachable token prediction with no user interaction; impersonation breaks confidentiality and integrity (C:H/I:H) but not availability.
Primary rating from Vendor (GitHub_M).
CVSS VectorVendor: GitHub_M
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N
Lifecycle Timeline
4DescriptionCVE.org
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.
Articles & Coverage 1
AnalysisAI
Session hijacking in BigBlueButton before 3.0.21 lets an authenticated conference participant predict and reuse other users' session tokens to impersonate them. The bbb-web component generated 16-character sessionToken values (and 12-character auth tokens and internal user IDs) using Apache Commons RandomStringUtils.randomAlphanumeric, a non-cryptographic PRNG, making the token space guessable to anyone who already holds a valid session. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The attacker must first hold a valid conference session on the target BigBlueButton server (PR:L) - i.e., be able to join a meeting as a participant - because prediction relies on the same weak java.util.Random-based generator that issues tokens for other users. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N, score 8.1) indicates network-reachable, low-complexity exploitation by an attacker who already holds low-level privileges - i.e., a legitimate session user, which matches the description of 'a session user' predicting others' tokens. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An attacker joins a meeting as an ordinary participant, obtaining a valid session and observing the format and values of issued tokens. Knowing that tokens come from a non-cryptographic java.util.Random, the attacker predicts another participant's (e.g., a moderator's) 16-character sessionToken and reuses it to impersonate that user within the conference. … |
| Remediation | Vendor-released patch: 3.0.21 - upgrade BigBlueButton to v3.0.21 or later, which replaces the insecure RandomStringUtils token generation with a java.security.SecureRandom-backed Util.randomAlphanumeric helper (fix commit 8457886c248aeba5597ee8749267602d6d117e98). … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, conduct a complete audit of BigBlueButton deployments to identify all systems running versions prior to 3.0.21, prioritizing instances that host sensitive or confidential communications. …
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