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CVE-2020-3580

KEVRansomware UseCisco ASA and FTD Cross-Site Scripting (XSS) Vulnerability

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.

Multiple vulnerabilities in the web services interface of Cisco Adaptive Security Appliance (ASA) Software and Cisco Firepower Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to conduct cross-site scripting (XSS) attacks against a user of the web services interface of an affected device. The vulnerabilities are due to insufficient validation of user-supplied input by the web services interface of an affected device. An attacker could exploit these vulnerabilities by persuading a user of the interface to click a crafted link. A successful exploit could allow the attacker to execute arbitrary script code in the context of the interface or allow the attacker to access sensitive, browser-based information. Note: These vulnerabilities affect only specific AnyConnect and WebVPN configurations. For more information, see the Vulnerable Products section.

CVSS 3.1 vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
PublishedOct 21, 2020
Last modifiedAug 11, 2026
Added to KEVNov 3, 2021
Remediation dueMay 3, 2022
    79
    Risk assessment · High

    Actively exploited and used by ransomware crews. Patch immediately.

    Exploitation
    Confirmed in the wild (CISA KEV)
    Federal remediation deadline
    Overdue by 1638 days
    Ransomware
    Used in known ransomware campaigns
    CVSS
    6.1 MEDIUM
    EPSS (30-day exploit probability)
    85.6% · top 1% of all CVEs
    Weakness
    CWE-79
    Attack vector
    Network, remotely reachable
    1. 1.Apply updates per vendor instructions.
    2. 2.Treat as emergency change: patch or isolate internet-facing instances first.
    3. 3.Review exposure: confirm which instances are reachable from the internet and restrict access until patched.
    4. 4.Hunt for compromise: review logs for the disclosure window, not just from the patch date.
    5. 5.Verify offline/immutable backups and segment the affected systems. This flaw is used for ransomware initial access.

    Assessment is derived automatically from the live signals above; verify against your own asset inventory.