CVE-2021-1566

HIGHNVD 7.47.4—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.4 under NVD CVSS v3. EPSS exploit probability: 0.7%, top 52% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
7.4
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.4Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

A vulnerability in the Cisco Advanced Malware Protection (AMP) for Endpoints integration of Cisco AsyncOS for Cisco Email Security Appliance (ESA) and Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to intercept traffic between an affected device and the AMP servers. This vulnerability is due to improper certificate validation when an affected device establishes TLS connections. A man-in-the-middle attacker could exploit this vulnerability by sending a crafted TLS packet to an affected device. A successful exploit could allow the attacker to spoof a trusted host and then extract sensitive information or alter certain API requests.

CVSS v3
7.4
EG Score
7.4(medium)
EG Risk
—
EPSS
48.2%
KEV
Not listed

Published

June 16, 2021

Last Modified

November 21, 2024

References (2)

Weakness Classification(2)

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

Data Freshness Timeline

(refreshed 9× in last 7d / 46× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-22 22:42 UTCEG score recompute
  2. 2026-07-22 14:05 UTCEPSS rescore
  3. 2026-07-21 15:22 UTCEPSS rescore
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  67. 2026-05-27 13:39 UTCEPSS rescore
  68. 2026-05-26 14:50 UTCEG score recompute
  69. 2026-05-26 14:49 UTCGHSA enrichment
  70. 2026-05-26 13:42 UTCEPSS rescore
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  74. 2026-05-24 16:49 UTCEPSS rescore

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-1566?
CVE-2021-1566 is a high vulnerability published on June 16, 2021. A vulnerability in the Cisco Advanced Malware Protection (AMP) for Endpoints integration of Cisco AsyncOS for Cisco Email Security Appliance (ESA) and Cisco Web Security Appliance (WSA) could allow an unauthenticated, remote attacker to intercept traffic between an affected device and the AMP…
When was CVE-2021-1566 disclosed?
CVE-2021-1566 was first published in the National Vulnerability Database on June 16, 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-2021-1566 actively exploited?
CVE-2021-1566 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 48.2% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-1566?
CVE-2021-1566 has a CVSS v3 base score of 7.4 (NVD).
How do I remediate CVE-2021-1566?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-1566, 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.

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