CVE-2021-4020: janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Script

Q: How do I fix CVE-2021-4020?

janus: upgrade to newer than 0.11.5. Exact commands for each OS are on this page.

Q: Is CVE-2021-4020 being exploited?

CVE-2021-4020 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2021-4020 affect?

CVE-2021-4020 affects janus. Severity is medium (CVSS 5.4). janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Q: How urgent is CVE-2021-4020?

Priority 38/100. Public exploit reference

Routine

MEDIUM 5.4UPGRADE

CVE-2021-4020 is a medium-severity flaw (CVSS 5.4) affecting janus. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Public exploit reference

A fixed release or distro patch exists.

Risk facts

CVSS score	5.4 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.8% (top 42%)
CISA exploited list	No
Weakness	CWE-79
Published	2021-11-27
Last modified	2026-06-17

Publisher (CNA): huntr.dev · Vendor: meetecho

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2021-11-27 10:15 UTCPublished CVE record published
2026-06-17 04:18 UTCUpdated Record last modified

meetecho janus UPGRADE

Affected: <= 0.11.5

Fixed in: newer than 0.11.5

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy janus || rpm -q janus || janus --version

2. UPGRADE to newer than 0.11.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade janus

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade janus

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2021-4020?

janus: upgrade to newer than 0.11.5. Exact commands for each OS are on this page.

Is CVE-2021-4020 being exploited?

CVE-2021-4020 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2021-4020 affect?

CVE-2021-4020 affects janus. Severity is medium (CVSS 5.4). janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

How urgent is CVE-2021-4020?

Priority 38/100. Public exploit reference

Related CVEs

CVE-2021-4124 MEDIUM 6.1 UPGRADE janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Script
CVE-2020-14034 CRITICAL 9.8 UPGRADE An issue was discovered in janus-gateway (aka Janus WebRTC Server) through 0.10.0
CVE-2020-14033 CRITICAL 9.8 UPGRADE An issue was discovered in janus-gateway (aka Janus WebRTC Server) through 0.10.0
CVE-2020-13901 CRITICAL 9.8 UPGRADE An issue was discovered in janus-gateway (aka Janus WebRTC Server) through 0.10.0
CVE-2020-13900 HIGH 7.5 UPGRADE An issue was discovered in janus-gateway (aka Janus WebRTC Server) through 0.10.0

References

← Back to latest CVEs