CVE-2021-4039

CRITICALNVD 9.89.8—Elevated

9.8

A command injection vulnerability in the web interface of the Zyxel NWA-1100-NH firmware could allow an attacker to execute arbitrary OS commands on the device.

CVSS v3: 9.8
EG Score: 9.8(medium)
EPSS: 98.8%
KEV: Not listed

Published

March 1, 2022

Last Modified

November 21, 2024

Advisory Details (2)

Auto-updated May 26, 2026

No patch confirmed yet.

generic

Support Download Page Redirect

https://www.zyxel.com/support/OS-command-injection-vulnerability-of-NWA1100-NH-access-point.shtml

generic

Packet Storm

http://packetstormsecurity.com/files/166752/Zyxel-NWA-1100-NH-Command-Injection.html

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

CWE-78OS Command Injection

Data Freshness Timeline

(refreshed 10× in last 7d / 13× in last 30d)

Every time one of our enrichment pipelines (NVD, MITRE cvelistV5, EPSS, CISA KEV, GHSA, OSV, vendor advisories) ran against this CVE. Most recent first.

2026-06-05 22:45 UTCepss_batch
2026-06-05 22:45 UTCepss_batch
2026-06-05 06:09 UTCepss_batch
2026-06-05 06:09 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-02 20:11 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-06-01 13:50 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-29 13:42 UTCepss_batch
2026-05-26 02:19 UTCEG score recompute
2026-05-26 02:19 UTCGHSA enrichment

Publicly available exploits

(1 reference)

Working exploit code is in the public domain (1 Exploit-DB entry). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

Exploit-DBEDB-50870
First seen Apr 19, 2022
Zyxel NWA-1100-NH - Command Injection
Open source ↗

Frequently asked(5)

What is CVE-2021-4039?

CVE-2021-4039 is a critical vulnerability published on March 1, 2022. A command injection vulnerability in the web interface of the Zyxel NWA-1100-NH firmware could allow an attacker to execute arbitrary OS commands on the device.

When was CVE-2021-4039 disclosed?

CVE-2021-4039 was first published in the National Vulnerability Database on March 1, 2022, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.

Is CVE-2021-4039 actively exploited?

CVE-2021-4039 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 98.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-4039?

CVE-2021-4039 has a CVSS v3 base score of 9.8 (NVD).

How do I remediate CVE-2021-4039?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-4039, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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CVE-2021-4039

📅 Published

🔄 Last Modified

📋 Advisory Details (2)