CVE-2026-27737Network attack vector

Stored XSS via unsanitized recorded chat HTML

Published May 18, 2026 · Updated May 18, 2026

Stored XSS in BigBlueButton before 3.0.19 allows remote authenticated users to execute script when a user replays a recording. The bbb-playback Text component passes stored public-chat HTML directly to React dangerouslySetInnerHTML without sanitizing it. A meeting participant must inject the chat content and a viewer must open the presentation-format recording, where the script runs in the playback origin and can read or alter browser-accessible data.

CVSS severity8.9
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Stored XSS in BigBlueButton before 3.0.19 allows remote authenticated users to execute script when a user replays a recording. The bbb-playback Text component passes stored public-chat HTML directly to React dangerouslySetInnerHTML without sanitizing it. A meeting participant must inject the chat content and a viewer must open the presentation-format recording, where the script runs in the playback origin and can read or alter browser-accessible data.

The record

CVE
CVE-2026-27737
Published
May 18, 2026
Updated
May 18, 2026
Vendor
Blindside Networks
Product
Scalelite
Classifications
CWE-79, T1059.007
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. May 18, 2026CVE publishedPublication date reported by the CVE source.
  2. May 18, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 1.7.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Blindside Networks · Scaleliteversion=< 1.7.0
BigBlueButton Inc. · BigBlueButtonversion=< 3.0.19
BigBlueButton Inc. · bbb-playbackversion=< 5.4.3

Published CVSS scores

8.9GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:L
6.5GitHub, Inc. CNACVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1059.007JavaScript/JScript

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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