CVE-2021-21777

CRITICALNVD 10.010.0—

10.0

An information disclosure vulnerability exists in the Ethernet/IP UDP handler functionality of EIP Stack Group OpENer 2.3 and development commit 8c73bf3. A specially crafted network request can lead to an out-of-bounds read.

CVSS v3: 10.0
EG Score: 10.0(medium)
EPSS: 57.2%
KEV: Not listed

Published

June 17, 2021

Last Modified

November 21, 2024

Advisory Details (1)

Auto-updated May 23, 2026

No patch confirmed yet.

generic

TALOS-2021-1234 || Cisco Talos Intelligence Group - Comprehensive Threat Intelligence

https://talosintelligence.com/vulnerability_reports/TALOS-2021-1234

Weakness Classification(1)

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

CWE-125Out-of-bounds Read

Data Freshness Timeline

(refreshed 15× in last 7d / 20× 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.

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Frequently asked(5)

What is CVE-2021-21777?

CVE-2021-21777 is a critical vulnerability published on June 17, 2021. An information disclosure vulnerability exists in the Ethernet/IP UDP handler functionality of EIP Stack Group OpENer 2.3 and development commit 8c73bf3. A specially crafted network request can lead to an out-of-bounds read.

When was CVE-2021-21777 disclosed?

CVE-2021-21777 was first published in the National Vulnerability Database on June 17, 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-2021-21777 actively exploited?

CVE-2021-21777 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 57.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.

What is the CVSS score of CVE-2021-21777?

CVE-2021-21777 has a CVSS v3 base score of 10.0 (NVD).

How do I remediate CVE-2021-21777?

Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-21777, 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-2021-21777

📅 Published

🔄 Last Modified

📋 Advisory Details (1)

TALOS-2021-1234 || Cisco Talos Intelligence Group - Comprehensive Threat Intelligence

Weakness Classification(1)

Data Freshness Timeline

❓ Frequently asked(5)

Dependency Blast Radius

Is Your Infrastructure Affected by CVE-2021-21777?

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Frequently asked(5)

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