CVE-2021-1566
HIGHDescription
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.
How to fix
TridentStack Control can deploy fixes like this automatically across your Windows, macOS, and Linux fleet. See how it works
Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.
CVSS v3 Vector
Exploitability
Impact
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
Exploit Intelligence
Moderate risk: more likely to be exploited than 49% of all known CVEs.
References
Related Vulnerabilities
Other CWE-296 vulnerabilities, ordered by exploit likelihood. View all
| CVE | Severity | CVSS | EPSS | Exploited | Fix |
|---|---|---|---|---|---|
| CVE-2021-44532 | Medium | 5.3 | 10% | - | Fix |
| CVE-2019-3890 | High | 8.1 | 1.0% | - | Fix |
| CVE-2019-3762 | High | 7.5 | 0.6% | - | - |
| CVE-2021-23155 | Critical | 9.0 | 0.5% | - | Fix |
| CVE-2026-44852 | High | 7.2 | 0.4% | - | Fix |
| CVE-2025-48057 | Critical | 9.8 | 0.4% | - | Fix |
Common questions
How do I fix CVE-2021-1566?
Upgrade asyncos to 12.5.1-043 or later.
Is CVE-2021-1566 being actively exploited?
Not that we know of. CVE-2021-1566 is not in the CISA Known Exploited Vulnerabilities catalog. Its EPSS score of 0.67% is the estimated probability that it will be exploited in the next 30 days. That is higher than 49% of all scored CVEs.
How severe is CVE-2021-1566?
CVE-2021-1566 has a CVSS v3 base score of 7.4, rated high. CVSS rates the technical impact if the vulnerability is exploited, not how likely that is, so weigh it alongside the exploit-prediction score when you decide what to patch first.
What does CVE-2021-1566 affect?
Published advisories record a fix for asyncos (NVD). Only products with a sourced advisory are listed, so treat this as what we can cite rather than a complete inventory.
Embed a live status badge for CVE-2021-1566
Markdown
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TridentStack Control continuously scans your Windows, macOS, and Linux fleet for known vulnerabilities, prioritizes them by severity and active exploitation, and patches them automatically.
This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2024-11-21.