CVE-2021-4020Public exploitNetwork attack vector

Stored XSS via unescaped demo metadata

Published Nov 27, 2021 · Updated Aug 3, 2024

Stored XSS in Meetecho Janus Gateway before 0.11.6 allows remote authenticated users to run script in demo users' browsers. Multiple demo scripts insert participant names, room or stream descriptions, and recording metadata into HTML without escaping angle brackets. A victim must open an affected demo after attacker-controlled data reaches it; the script runs in that page's origin and can read or alter browser-visible data.

CVSS severity5.4
Medium
EPSS probability0.82%
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 Meetecho Janus Gateway before 0.11.6 allows remote authenticated users to run script in demo users' browsers. Multiple demo scripts insert participant names, room or stream descriptions, and recording metadata into HTML without escaping angle brackets. A victim must open an affected demo after attacker-controlled data reaches it; the script runs in that page's origin and can read or alter browser-visible data.

The record

CVE
CVE-2021-4020
Published
Nov 27, 2021
Updated
Aug 3, 2024
Vendor
Meetecho
Product
Janus Gateway
Classifications
CWE-79, T1189
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Nov 27, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record 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=unspecified <0.11.6

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

Meetecho · Janus Gatewayversion=unspecified <0.11.6

Published CVSS scores

8.8huntr.devCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
5.4NIST NVDCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
3.5NIST NVDAV:N/AC:M/Au:S/C:N/I:P/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 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
T1189Drive-by Compromise

Public exploit references

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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