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Known exploited · Cisco

CVE-2020-3580: Cisco ASA and FTD Cross-Site Scripting (XSS) Vulnerability

What it is

Cisco Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) contain an insufficient input validation vulnerability for user-supplied input by the web services interface. Successful exploitation could allow an attacker to perform cross-site scripting (XSS) in the context of the interface or access sensitive browser-based information.

Added November 3, 2021Due May 3, 2022CISA KEV catalog 2026.10.01

Vendor
Cisco
Product
Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD)
Added to KEV
November 3, 2021
CISA due date
May 3, 2022
Ransomware use
Known

What CISA requires

Apply updates per vendor instructions.

Forensic triage

No

What to do now

  1. Find every instance of Adaptive Security Appliance (ASA) and Firepower Threat Defense (FTD) you run, including the forgotten ones, and check its version against the vendor advisory.
  2. Apply the vendor's fix or mitigation, before May 3, 2022 if you are bound by CISA's deadline, sooner if it faces the internet.
  3. Assume it was tried against you already: look for signs of exploitation from the date it was added, not from the day you patched.
  4. Until every instance is patched, block the attack at the edge: a WAF in blocking mode stops cross-site scripting payloads.

References

CVE-2020-3580 in the National Vulnerability Database

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Block it at the edge while you patch

The Dome's WAF runs the OWASP Core Rule Set in blocking mode and stops cross-site scripting payloads before they reach your application.

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Source: CISA Known Exploited Vulnerabilities Catalog (public domain), catalog version 2026.10.01.