How severe is CVE-2021-4020?

CVE-2021-4020 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-4020 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-4020?

CVE-2021-4020 affects Meetecho Janus. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-4020?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-4020 published?

CVE-2021-4020 was published on 2021-11-27 and last updated on 2026-06-17.

CVE-2021-4020

CVE-2021-4020 is a medium-severity vulnerability in Meetecho Janus with a CVSS 3.x base score of 5.4. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 3.x base score 5.4)
CVSS v2: 3.5
EPSS exploit prediction: 1% (53rd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Meetecho Janus
Published: 2021-11-27
Last modified: 2026-06-17

Description

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

Frequently asked questions

What is CVE-2021-4020?: janus-gateway is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
How severe is CVE-2021-4020?: CVE-2021-4020 has a CVSS 3.x base score of 5.4, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-4020 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (53rd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-4020?: CVE-2021-4020 affects Meetecho Janus. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-4020?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-4020 published?: CVE-2021-4020 was published on 2021-11-27 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:meetecho:janus:*:*:*:*:*:*:*:*

More vulnerabilities in Meetecho Janus

CVE-2020-14034 — Critical (CVSS 9.8): An issue was discovered in janus-gateway (aka Janus WebRTC Server) through 0.10.0. janus_get_codec_from_pt in utils.c…
CVE-2020-14033 — Critical (CVSS 9.8): An issue was discovered in janus-gateway (aka Janus WebRTC Server) through 0.10.0. janus_streaming_rtsp_parse_sdp in…
CVE-2020-13901 — Critical (CVSS 9.8): An issue was discovered in janus-gateway (aka Janus WebRTC Server) through 0.10.0. janus_sdp_merge in sdp.c has a…
CVE-2020-10574 — Critical (CVSS 9.8): An issue was discovered in Janus through 0.9.1. janus.c tries to use a string that doesn't actually exist during a…
CVE-2020-13900 — High (CVSS 7.5): An issue was discovered in janus-gateway (aka Janus WebRTC Server) through 0.10.0. janus_sdp_preparse in sdp.c has a…
CVE-2020-13899 — High (CVSS 7.5): An issue was discovered in janus-gateway (aka Janus WebRTC Server) through 0.10.0. janus_process_incoming_request in…

All CVEs affecting Meetecho Janus →

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