⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Critical · CVSS 9.8 ⚠ ACTIVELY EXPLOITED — CISA KEV

How to Fix CVE-2020-5902: RCE in BIG-IP

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

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 9.8, Critical
Actively exploited?Yes, listed in CISA KEV (added 2021-11-03)
AffectedBIG-IP (15.0.0-15.1.0.3, 14.1.0-14.1.2.5, 13.1.0-13.1.3.3, 12.1.0-12.1.5.1, 11.6.1-11.6.5.1)
Fixed inSee vendor advisory
Type (CWE)RCE
⚠️ Patch immediately. CVE-2020-5902 is in CISA's Known Exploited Vulnerabilities catalog (added 2021-11-03). Federal agencies had until 2022-05-03 to remediate.

What is CVE-2020-5902?

In BIG-IP versions 15.0.0-15.1.0.3, 14.1.0-14.1.2.5, 13.1.0-13.1.3.3, 12.1.0-12.1.5.1, and 11.6.1-11.6.5.1, the Traffic Management User Interface (TMUI), also referred to as the Configuration utility, has a Remote Code Execution (RCE) vulnerability in undisclosed pages.

In practical terms, a successful attacker gets remote code execution on the affected system. CISA has confirmed exploitation in the wild, so this is not a theoretical risk.

Am I affected?

You're affected if you run F5 BIG-IP at any version in the Affected row above. Use these probes to find your installed build:


tmsh show /sys version

How to fix CVE-2020-5902

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.

F5 BIG-IP (tmsh)


# Vendor advisory: https://support.f5.com/csp/article/K52145254
tmsh show /sys version
tmsh save /sys ucs /var/local/ucs/pre-upgrade-$(date +%Y%m%d).ucs
# Upload BIGIP-<patched-version>.iso, then install to an empty volume:
tmsh install /sys software image BIGIP-<patched-version>.iso volume HD1.2 create-volume
tmsh show /sys software
tmsh reboot volume HD1.2

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


# Vendor advisory: https://support.f5.com/csp/article/K52145254
# Run as Administrator
$ErrorActionPreference = 'Stop'
$log = "$env:ProgramData\BIGIP-Patch-CVE-2020-5902.log"
function Write-Log($msg) { "$(Get-Date -Format s)  $msg" | Tee-Object -FilePath $log -Append }

Write-Log "Starting CVE-2020-5902 remediation for F5 BIG-IP"

# 1. Detect: replace the path/version probe with one valid for your install
$installed = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*BIG-IP*' } |
    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\BIGIP-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\F5\BIG-IP"
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\BIGIP-<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 { $_.Name -like '*BIG-IP*' } |
    Select-Object -First 1 -ExpandProperty Version)
if ([version]$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://support.f5.com/csp/article/K52145254
#!/usr/bin/env bash
set -euo pipefail
LOG=/var/log/big-ip-patch-cve-2020-5902.log
log()  { echo "$(date -Iseconds)  $*" | tee -a "$LOG"; }

log "Starting CVE-2020-5902 remediation for F5 BIG-IP"

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

# 2. Backup config
BACKUP=/var/backups/big-ip-$(date +%Y%m%d-%H%M)
mkdir -p "$BACKUP"
for d in /etc/big-ip /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 big-ip
else
    sudo dnf upgrade --security -y big-ip
fi

# 4. Verify
if [ "$PKG_MGR" = apt ]; then
    NEW=$(dpkg-query -W -f='${Version}' big-ip)
else
    NEW=$(rpm -q --queryformat '%{VERSION}' big-ip)
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."

Marquee detail: f5 big-ip TMUI RCE

CVE-2020-5902 is an unauthenticated remote code execution in the Traffic Management User Interface (TMUI) of F5 BIG-IP. A crafted URL containing ; allows the attacker to reach internal Tomcat handlers and run arbitrary commands as root. Patch to the F5-listed fixed builds for every train you run.

Detection (probe your own appliance)


# From a jump host on the management subnet
curl -ks "https://<bigip-mgmt-ip>/tmui/login.jsp/..;/tmui/locallb/workspace/fileRead.jsp?fileName=/etc/passwd" -o /tmp/probe.html
if grep -q '^root:' /tmp/probe.html; then
    echo "VULNERABLE: TMUI exposed /etc/passwd"
else
    echo "Not vulnerable via fileRead.jsp"
fi

Pre-patch httpd workaround (run as root on the BIG-IP)


tmsh modify sys httpd include "Location /tmui/login.jsp/..;\nRedirect 404 /tmui/login.jsp/..\n/Location\nLocation /hsqldb\nRedirect 404 /hsqldb\n/Location"
tmsh save sys config
tmsh restart sys service httpd

Restrict TMUI to the management network


tmsh modify sys httpd allow add { 10.0.0.0/24 }
tmsh modify sys sshd allow add { 10.0.0.0/24 }
tmsh save sys config

Verify after upgrade


tmsh show /sys version
curl -ks "https://<bigip-mgmt-ip>/tmui/login.jsp/..;/tmui/locallb/workspace/fileRead.jsp?fileName=/etc/passwd" -o - | head -1
# Expected after patch: an HTML error page, NOT the contents of /etc/passwd

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.

Block external access to the affected service

Apply a perimeter ACL so the exploitable port is only reachable from administrative subnets:


# Vendor advisory: https://support.f5.com/csp/article/K52145254
# Example Cisco ACL on the upstream router
access-list 110 permit tcp 10.0.0.0 0.0.0.255 host <appliance-ip> eq 443
access-list 110 deny   tcp any host <appliance-ip> eq 443 log
interface GigabitEthernet0/0
 ip access-group 110 in

Rate-limit and log the affected endpoint at the reverse proxy


limit_req_zone $binary_remote_addr zone=admin:10m rate=10r/m;
location /<vulnerable-path> {
    limit_req zone=admin burst=5 nodelay;
    access_log /var/log/nginx/admin-access.log combined;
    proxy_pass http://backend;
}

How to verify the fix worked

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


tmsh show /sys version

Expected output: a row reading Version the patched build (or higher) under Main Package.

Then re-run any vulnerability scanner you used previously and confirm the finding for CVE-2020-5902 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-2020-5902 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-2020-5902?

CVSS rates it 9.8 (Critical). Use that score to set your patch priority next to the other items in your queue.

Do I have to take BIG-IP 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-2020-5902 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.*