CVE-2021-4020

Cross-site Scripting (XSS) - Stored in meetecho/janus-gateway

8.8 HighFix available

janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Attack profile

How easy it is to exploit

Attack vector: Network
Complexity: Low
Privileges needed: Low
User interaction: None

What an attacker can affect

Confidentiality: High
Integrity: High
Availability: High

Exploit likelihood

0.84%Up 0.2 points since Nov 28, 2021

What each source reports

CVE List Score used 8.8

Cross-site Scripting (XSS) - Stored in meetecho/janus-gateway

janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Record: CVE-2021-4020
CVSS 3.0: 8.8 HighCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Weakness: CWE-79
Updated: 2026-11-02

EUVDEUVD-2021-33923 8.8

janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Record: EUVD-2021-33923
CVSS 3.0: 8.8 HighCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-03

GitHub AdvisoriesGHSA-cq47-8w25-m65v No score

janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation (...

janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Record: GHSA-cq47-8w25-m65v
Weakness: CWE-79
Updated: 2026-11-02

NVD 5.4

janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Record: CVE-2021-4020
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
CVSS 3.0: 8.8 HighCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0: 3.5 LowAV:N/AC:M/Au:S/C:N/I:P/A:N
Weakness: CWE-79
Updated: 2026-11-02

OSV 5.4

janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Record: CVE-2021-4020
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Updated: 2026-11-02

OSVDEBIAN-CVE-2021-4020 5.4

janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Record: DEBIAN-CVE-2021-4020
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
Updated: 2026-11-02

OSVUBUNTU-CVE-2021-4020 5.4

janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Record: UBUNTU-CVE-2021-4020
CVSS 3.1: 5.4 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
CVSS 3.0: 8.8 HighCVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Updated: 2026-11-02

OSVopenSUSE-SU-2024:11675-1 No score

janus-gateway-0.11.6-1.1 on GA media

These are all security issues fixed in the janus-gateway-0.11.6-1.1 package on the GA media of openSUSE Tumbleweed.

Record: openSUSE-SU-2024:11675-1
Updated: 2026-11-02

Affected products

Affected packages

Affected packages
Package	Affected	Fixed
`janus` Debian:12	before 0.11.5-4	0.11.5-4
`janus` Debian:14	before 0.11.5-4, plus listed versions 0.10.0-10.10.1-10.10.2-10.10.3-10.10.4-1 Show 45 moreShow less 0.10.5-10.10.6-10.10.7-10.10.8-10.10.8-20.10.9-10.10.9-20.11.1-10.11.2-10.11.3-1~exp10.11.4-10.11.5-10.11.5-20.11.5-30.2.2+dfsg-10.2.2+dfsg-20.2.2+dfsg-30.2.2+dfsg-40.2.2+dfsg-5~exp10.2.2+dfsg-5~exp20.2.2+dfsg-5~exp30.2.3-10.2.4-10.2.4-20.2.5-10.2.6-10.3.1-10.4.2-10.4.4-10.4.5-10.4.5-20.5.0-10.6.0-10.6.0-20.6.1-10.6.2-10.6.3-10.7.2-10.7.2-20.7.3-10.7.3-20.9.1+20200313-10.9.1-10.9.2-10.9.2-1~bpo10+1	0.11.5-4
`janus` Ubuntu:18.04:LTS	All versions, plus listed versions 0.2.4-20.2.5-10.2.6-10.2.6-1build10.2.6-1build2	None known
`janus` Ubuntu:20.04:LTS	All versions, plus listed versions 0.7.3-20.7.3-2build1	None known
`janus` Ubuntu:22.04:LTS	All versions, plus listed versions 0.11.2-10.11.5-10.11.5-1ubuntu10.11.5-30.11.5-4 Show 5 moreShow less 0.11.6-10.11.7-10.11.8-10.11.8-20.11.8-3	None known

History

History
Recorded	Changed	Sources
Nov 3, 2026	aliases	EUVD
Nov 2, 2026	first indexed	CVE List, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-4020 is a high vulnerability (CVSS 8.8) in Meetecho Janus, published November 27, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.84%, the 58th percentile. Fixed in janus 0.11.5-4.

References

This page doesn't list everything

Left out here: 3 versions. The JSON record has them.