⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Medium · CVSS 6.1 ⚠ ACTIVELY EXPLOITED — CISA KEV

How to Fix CVE-2020-3580: Cross-Site Scripting in Cisco Adaptive Security Appliance (ASA) Software

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 6.1, Medium
Actively exploited?Yes, listed in CISA KEV (added 2021-11-03)
AffectedCisco Adaptive Security Appliance (ASA) Software (n/a)
Fixed inSee vendor advisory
Type (CWE)CWE-79
⚠️ Patch immediately. CVE-2020-3580 is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03). Federal agencies had until 2022-05-03 to remediate.

What is CVE-2020-3580?

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.

In practical terms, a successful attacker gets execution of attacker-controlled JavaScript in a victim's browser. CISA has confirmed exploitation in the wild, so this is not a theoretical risk.

Am I affected?

You're affected if you run Cisco Adaptive Security Appliance (ASA) Software at any version in the Affected row above. Use these probes to find your installed build:


show version | include Version

How to fix CVE-2020-3580

The primary fix is to upgrade to the patched build listed in the Fixed in row above (See vendor advisory). Pick the platform that matches your install and run the commands below.

Cisco IOS / IOS XE / IOS XR (CLI)


# Vendor advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-xss-multiple-FCB3vPZe
enable
# Confirm running image and version
show version | include Version
# Stage the patched image (use the verified build from the advisory, e.g. <patched-version>)
copy ftp://upload-server/cisco-adaptive-security-appliance-(asa)-software-<patched-version>.bin flash:
# Make the new image the boot image
configure terminal
 boot system flash:cisco-adaptive-security-appliance-(asa)-software-<patched-version>.bin
 end
write memory
reload

Cisco ASA / FTD (ASDM or CLI upgrade)


# Vendor advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-xss-multiple-FCB3vPZe
enable
show version
copy tftp://10.0.0.10/asa<patched-version>-smp-k8.bin disk0:
configure terminal
 boot system disk0:/asa<patched-version>-smp-k8.bin
 end
write memory
reload

PowerShell script (Windows) - detect, back up, upgrade, verify, log


# Vendor advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-xss-multiple-FCB3vPZe
# Run as Administrator
$ErrorActionPreference = 'Stop'
$log = "$env:ProgramData\CiscoAdaptiveSecurityApplianceASASoftware-Patch-CVE-2020-3580.log"
function Write-Log($msg) { "$(Get-Date -Format s)  $msg" | Tee-Object -FilePath $log -Append }

Write-Log "Starting CVE-2020-3580 remediation for Cisco Cisco Adaptive Security Appliance (ASA) Software"

# 1. Detect: replace the path/version probe with one valid for your install
$installed = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*Cisco*' } |
    Select-Object -First 1 -ExpandProperty Version)
Write-Log "Detected version: $installed"

if (-not $installed) {
    Write-Log "Product not installed on this host; nothing to do."
    return
}
if ([version]$installed -ge [version]'<patched-version>') {
    Write-Log "Already at fixed version $installed; no action needed."
    return
}

# 2. Backup configuration to a timestamped folder
$backup = "$env:ProgramData\CiscoAdaptiveSecurityApplianceASASoftware-Backup-$(Get-Date -Format yyyyMMdd-HHmm)"
New-Item -ItemType Directory -Path $backup -Force | Out-Null
# Adjust the source path to match your install
$src = "$env:ProgramFiles\Cisco\Cisco Adaptive Security Appliance (ASA) Software"
if (Test-Path $src) { Copy-Item -Path $src -Destination $backup -Recurse -Force }
Write-Log "Backed up config to $backup"

# 3. Apply the patched installer (place the verified file on a share or staging path)
$installer = "$env:TEMP\CiscoAdaptiveSecurityApplianceASASoftware-<patched-version>.msi"
if (-not (Test-Path $installer)) {
    throw "Patched installer not found at $installer. Stage it from your software repo first."
}
Start-Process msiexec.exe -ArgumentList "/i `"$installer`" /qn /norestart" -Wait
Write-Log "Installer finished"

# 4. Verify
$verify = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*Cisco*' } |
    Select-Object -First 1 -ExpandProperty Version)
if ([version]$verify -ge [version]'<patched-version>') {
    Write-Log "SUCCESS: now at $verify (>= <patched-version>)"
} else {
    Write-Log "FAILURE: still at $verify after install"
    exit 1
}

Bash script (Linux) - detect, back up, upgrade, verify, log


# Vendor advisory: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-asaftd-xss-multiple-FCB3vPZe
#!/usr/bin/env bash
set -euo pipefail
LOG=/var/log/cisco-adaptive-security-appliance--asa--software-patch-cve-2020-3580.log
log()  { echo "$(date -Iseconds)  $*" | tee -a "$LOG"; }

log "Starting CVE-2020-3580 remediation for Cisco Cisco Adaptive Security Appliance (ASA) Software"

# 1. Detect installed version (works for deb and rpm packages)
if command -v dpkg >/dev/null && dpkg -s cisco-adaptive-security-appliance--asa--software >/dev/null 2>&1; then
    CURRENT=$(dpkg-query -W -f='${Version}' cisco-adaptive-security-appliance--asa--software)
    PKG_MGR=apt
elif command -v rpm >/dev/null && rpm -q cisco-adaptive-security-appliance--asa--software >/dev/null 2>&1; then
    CURRENT=$(rpm -q --queryformat '%{VERSION}' cisco-adaptive-security-appliance--asa--software)
    PKG_MGR=dnf
else
    log "cisco-adaptive-security-appliance--asa--software not installed via apt or rpm; check your package manager or vendor instructions."
    exit 0
fi
log "Detected: cisco-adaptive-security-appliance--asa--software=$CURRENT (manager=$PKG_MGR)"

# 2. Backup config
BACKUP=/var/backups/cisco-adaptive-security-appliance--asa--software-$(date +%Y%m%d-%H%M)
mkdir -p "$BACKUP"
for d in /etc/cisco-adaptive-security-appliance--asa--software /etc/${pkg%%-*} ; do
    [ -d "$d" ] && cp -a "$d" "$BACKUP/" && log "Backed up $d to $BACKUP"
done

# 3. Upgrade
if [ "$PKG_MGR" = apt ]; then
    sudo apt-get update -y
    sudo apt-get install --only-upgrade -y cisco-adaptive-security-appliance--asa--software
else
    sudo dnf upgrade --security -y cisco-adaptive-security-appliance--asa--software
fi

# 4. Verify
if [ "$PKG_MGR" = apt ]; then
    NEW=$(dpkg-query -W -f='${Version}' cisco-adaptive-security-appliance--asa--software)
else
    NEW=$(rpm -q --queryformat '%{VERSION}' cisco-adaptive-security-appliance--asa--software)
fi
log "After upgrade: $NEW"

# Optionally compare against <patched-version> with dpkg --compare-versions or sort -V
log "Done. Restart the affected service if the package install did not."

If you can't patch immediately

These are runnable hardening commands. They reduce blast radius but they're not a replacement for the vendor patch.

Tighten the Content-Security-Policy and cookie flags


add_header Content-Security-Policy "default-src 'self'; script-src 'self'" always;
add_header X-Frame-Options DENY always;
add_header X-Content-Type-Options nosniff always;

How to verify the fix worked

Run the version probe again and confirm the running build matches the Fixed in row above.


show version | include Version

Expected output: a line that includes the patched build (for example Version the patched build or higher).

Then re-run any vulnerability scanner you used previously and confirm the finding for CVE-2020-3580 has cleared. Sweep your logs for the indicators of compromise listed in the vendor or CISA advisory, especially if the system was internet-reachable during the disclosure window.

Frequently asked questions

Is CVE-2020-3580 being actively exploited?

Yes. CISA added it to the Known Exploited Vulnerabilities catalog, which means in-the-wild exploitation has been observed and confirmed.

How severe is CVE-2020-3580?

CVSS rates it 6.1 (Medium). Use that score to set your patch priority next to the other items in your queue.

Do I have to take Cisco Adaptive Security Appliance (ASA) Software offline to apply the patch?

It depends on the deployment. High-availability or clustered installs can usually patch one node at a time with no full outage. Standalone installs typically need a short restart. Always follow the vendor's documented upgrade steps.

What if my vulnerability scanner still flags CVE-2020-3580 after I patch?

Re-run the scan after a service restart, then confirm the scanner's plugin set is up to date. Some scanners detect by banner version only and lag the official fix metadata by a release.

References

*Written by Sai Kiran Pandrala on 2026-05-25. Sourced from the official vendor advisory, the NVD record, and the CISA KEV listing. Always confirm against the vendor advisory before applying changes in production.*