CVE-2021-20042

CRITICALNVD 9.89.8—Trending — 4 sources updated this week

9.8

An unauthenticated remote attacker can use SMA 100 as an unintended proxy or intermediary undetectable proxy to bypass firewall rules. This vulnerability affected SMA 200, 210, 400, 410 and 500v appliances.

CVSS v3: 9.8
EG Score: 9.8(medium)
EPSS: 68.5%
KEV: Not listed

Published

December 8, 2021

Last Modified

November 21, 2024

References (2)

PSIRT@sonicwallhttps://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0026
af854a3a-2127-422b-91ae-364da2661108https://psirt.global.sonicwall.com/vuln-detail/SNWLID-2021-0026

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 15× in last 7d / 16× 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.

2026-05-31 22:29 UTCepss_batch
2026-05-31 22:29 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-31 00:15 UTCepss_batch
2026-05-29 13:42 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-28 13:43 UTCepss_batch
2026-05-27 13:39 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 06:45 UTCEG score recompute
2026-05-26 06:45 UTCGHSA enrichment
2026-05-26 02:16 UTCOSV refresh
2026-05-24 16:49 UTCepss_batch

Frequently asked(5)

What is CVE-2021-20042?

CVE-2021-20042 is a critical vulnerability published on December 8, 2021. An unauthenticated remote attacker can use SMA 100 as an unintended proxy or intermediary undetectable proxy to bypass firewall rules. This vulnerability affected SMA 200, 210, 400, 410 and 500v appliances.

When was CVE-2021-20042 disclosed?

CVE-2021-20042 was first published in the National Vulnerability Database on December 8, 2021, 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-2021-20042 actively exploited?

CVE-2021-20042 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 68.5% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-20042?

CVE-2021-20042 has a CVSS v3 base score of 9.8 (NVD).

How do I remediate CVE-2021-20042?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-20042, 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-2021-20042

📅 Published

🔄 Last Modified

🔗 References (2)

Weakness Classification(2)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-20042?

🔗 Related CVEs(same CWE)

Same CWE

Published

Last Modified

References (2)

Frequently asked(5)

Related CVEs(same CWE)