CVE-2021-4234

HIGHNVD 7.57.5—

7.5

OpenVPN Access Server 2.10 and prior versions are susceptible to resending multiple packets in a response to a reset packet sent from the client which the client again does not respond to, resulting in a limited amplification attack.

CVSS v3: 7.5
EG Score: 7.5(medium)
EPSS: 60.2%
KEV: Not listed

Published

July 6, 2022

Last Modified

November 21, 2024

References (2)

security@openvpnhttps://openvpn.net/vpn-server-resources/release-notes/#openvpn-access-server-2-11-0
af854a3a-2127-422b-91ae-364da2661108https://openvpn.net/vpn-server-resources/release-notes/#openvpn-access-server-2-11-0

Weakness Classification(1)

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

CWE-406

Data Freshness Timeline

(refreshed 10× in last 7d / 19× 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.

2026-06-02 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 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
2026-05-27 13:39 UTCepss_batch
2026-05-26 13:43 UTCepss_batch
2026-05-26 13:42 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-26 07:17 UTCepss_batch
2026-05-25 19:23 UTCEG score recompute
2026-05-25 19:23 UTCGHSA enrichment
2026-05-24 00:53 UTCOSV refresh

Frequently asked(5)

What is CVE-2021-4234?

CVE-2021-4234 is a high vulnerability published on July 6, 2022. OpenVPN Access Server 2.10 and prior versions are susceptible to resending multiple packets in a response to a reset packet sent from the client which the client again does not respond to, resulting in a limited amplification attack.

When was CVE-2021-4234 disclosed?

CVE-2021-4234 was first published in the National Vulnerability Database on July 6, 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-2021-4234 actively exploited?

CVE-2021-4234 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 60.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-4234?

CVE-2021-4234 has a CVSS v3 base score of 7.5 (NVD).

How do I remediate CVE-2021-4234?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-4234, 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-2021-4234

📅 Published

🔄 Last Modified

🔗 References (2)