⚠ 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 10 ⚠ ACTIVELY EXPLOITED — CISA KEV

How to Fix CVE-2019-11708: Improper Input Validation in Mozilla Firefox and Thunderbird

By Sai Kiran Pandrala

⚡ At a glance
SeverityCVSS 10 (Critical)
Actively exploited?Yes, listed in CISA KEV (added 2022-05-23, federal due date 2022-06-13)
AffectedFirefox ESR: before 60.7.2; Firefox: before 67.0.4; Thunderbird: before 60.7.2
Fixed inFirefox ESR: 60.7.2 and later; Firefox: 67.0.4 and later; Thunderbird: 60.7.2 and later
Type (CWE)CWE-20: Improper Input Validation
Actively exploited. Listed in the CISA Known Exploited Vulnerabilities catalog since 2022-05-23; federal civilian agencies must remediate by 2022-06-13. Patch on an emergency cycle if the system is internet-exposed.

What is CVE-2019-11708?

Insufficient vetting of parameters passed with the Prompt:Open IPC message between child and parent processes can result in the non-sandboxed parent process opening web content chosen by a compromised child process. When combined with additional vulnerabilities this could result in executing arbitrary code on the user's computer. This vulnerability affects Firefox ESR < 60.7.2, Firefox < 67.0.4, and Thunderbird < 60.7.2.

A successful exploit gives the attacker the impact described in the vendor advisory. The fix is to install the patched build of Mozilla Firefox and Thunderbird listed in the table above, then confirm the running version after the upgrade.

Am I affected?

Check your installed version of Mozilla Firefox and Thunderbird against the Affected row above. If the build sits inside any of those ranges, treat the host as vulnerable until patched.

Read the version the same way you would for any maintenance task: the management console About page, the CLI version command, or the package manager record for the installed binary. The vendor advisory linked in the references is the authoritative source for the affected-build matrix.

How to fix CVE-2019-11708

The remediation is the patched build of Mozilla Firefox and Thunderbird. The blocks below give you runnable commands for the platforms that ship this product, plus a full PowerShell and Bash script you can drop into your patch automation.

Linux (Firefox / Thunderbird)


sudo apt-get update
sudo apt-get install --only-upgrade firefox firefox-esr
firefox --version
# RHEL / Fedora
sudo dnf upgrade firefox --security -y

Windows (PowerShell)


winget upgrade --id Mozilla.Firefox --accept-source-agreements --accept-package-agreements
(Get-Item "$env:ProgramFiles\Mozilla Firefox\firefox.exe").VersionInfo.ProductVersion

macOS


brew upgrade --cask firefox thunderbird

Full PowerShell remediation script (detect, back up, patch, verify, log)


<#
.SYNOPSIS  Remediates CVE-2019-11708 on Windows hosts.
.DESCRIPTION
  Detects current version of Firefox and Thunderbird, takes a config backup, applies the patched build
  (60.7.2), confirms the upgrade, and writes a transcript to %ProgramData%\Patching.
#>
$ErrorActionPreference = 'Stop'
$logDir = "$env:ProgramData\Patching"
New-Item -ItemType Directory -Force -Path $logDir | Out-Null
Start-Transcript -Path "$logDir\CVE-2019-11708-$(Get-Date -Format yyyyMMdd-HHmmss).log"

try {
    Write-Host '[1/5] Detecting current version'
    $svc = Get-Service | Where-Object { $_.DisplayName -match 'Firefox' } | Select-Object -First 1
    if ($svc) { Write-Host "  Service: $($svc.Name) state=$($svc.Status)" }

    Write-Host '[2/5] Backup config directory if present'
    $cfg = "$env:ProgramFiles\Firefox"
    if (Test-Path $cfg) {
        $bak = "$logDir\CVE-2019-11708-backup-$(Get-Date -Format yyyyMMdd-HHmmss).zip"
        Compress-Archive -Path $cfg -DestinationPath $bak -Force
        Write-Host "  Backup -> $bak"
    }

    Write-Host '[3/5] Apply patch'
    try {
        winget upgrade --id <vendor.Firefox> --accept-source-agreements --accept-package-agreements --silent
    } catch {
        Write-Warning "winget upgrade failed: $_  -- falling back to MSU/MSI installer"
        Start-Process msiexec.exe -ArgumentList '/i "C:\Temp\patched.msi" /qn /norestart' -Wait
    }

    Write-Host '[4/5] Verify version'
    Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5
    # Adapt the next line to your product's version file:
    Get-ChildItem "$env:ProgramFiles\Firefox" -Recurse -Filter *.exe -ErrorAction SilentlyContinue |
        Select-Object -First 1 | ForEach-Object { $_.VersionInfo.FileVersion }

    Write-Host '[5/5] Restart service if needed'
    if ($svc) { Restart-Service $svc.Name }
    Write-Host "CVE-2019-11708 remediation complete"
} catch {
    Write-Error "CVE-2019-11708 remediation FAILED: $_"
    exit 1
} finally {
    Stop-Transcript
}

Full Bash remediation script (detect, back up, patch, verify, log)


#!/usr/bin/env bash
# remediate-cve-2019-11708.sh — detect, back up, patch, verify.
set -euo pipefail
LOG="/var/log/patching"
mkdir -p "$LOG"
STAMP="$(date +%Y%m%d-%H%M%S)"
LOGFILE="$LOG/CVE-2019-11708-$STAMP.log"
exec > >(tee -a "$LOGFILE") 2>&1

echo "[1/5] Detect installed Firefox and Thunderbird"
if command -v dpkg >/dev/null 2>&1; then
    dpkg -l | grep -i "firefox" || true
elif command -v rpm >/dev/null 2>&1; then
    rpm -qa | grep -i "firefox" || true
fi

echo "[2/5] Backup config"
for d in /etc/firefox /opt/firefox /usr/local/firefox; do
    if [[ -d "$d" ]]; then
        tar czf "$LOG/CVE-2019-11708-$(basename $d)-$STAMP.tgz" "$d"
        echo "  Backup -> $LOG/CVE-2019-11708-$(basename $d)-$STAMP.tgz"
    fi
done

echo "[3/5] Apply patch (target: 60.7.2)"
if command -v apt-get >/dev/null 2>&1; then
    sudo apt-get update
    sudo apt-get install --only-upgrade "firefox" -y
elif command -v dnf >/dev/null 2>&1; then
    sudo dnf upgrade "firefox" --security -y
elif command -v yum >/dev/null 2>&1; then
    sudo yum update "firefox" --security -y
elif command -v zypper >/dev/null 2>&1; then
    sudo zypper patch --category security
fi

echo "[4/5] Verify"
if systemctl status "firefox" >/dev/null 2>&1; then
    sudo systemctl restart "firefox"
    systemctl is-active "firefox"
fi
command -v "firefox" >/dev/null 2>&1 && "firefox" --version || true

echo "[5/5] CVE-2019-11708 remediation script complete. Log: $LOGFILE"

If you can't patch immediately

If you cannot patch in the maintenance window, restrict access to the affected service to a small admin allowlist at the network edge, disable the affected feature if it is not in use, and monitor the relevant logs for the exploitation indicators referenced in the vendor advisory.

Allowlist the service at the firewall


# Vendor advisory: https://security.gentoo.org/glsa/201908-12
# Linux iptables example
sudo iptables -A INPUT -p tcp --dport <port> -s <admin-cidr> -j ACCEPT
sudo iptables -A INPUT -p tcp --dport <port> -j DROP


# Vendor advisory: https://security.gentoo.org/glsa/201908-12
New-NetFirewallRule -DisplayName 'Restrict-CVE-2019-11708-port' -Direction Inbound -Action Block -Protocol TCP -LocalPort <port>
New-NetFirewallRule -DisplayName 'Allow-CVE-2019-11708-admin' -Direction Inbound -Action Allow -Protocol TCP -LocalPort <port> -RemoteAddress 10.0.0.0/24

How to verify the fix worked

  1. Re-run the version command from the fix section. The output must match the patched build listed in the vendor advisory for your branch.
  2. Re-run an authenticated vulnerability scan (Nessus, Qualys, OpenVAS, Defender Vulnerability Management) targeting the patched host. CVE-2019-11708 must no longer be reported.
  3. Pull the latest service logs and search for the exploitation signatures in the vendor advisory. Treat any match before the patch timestamp as a possible compromise: isolate the host, rotate credentials the affected process could see, and run a full IR triage.
  4. Confirm any compensating control you put in place (firewall rules, sysctl, registry edits) is either intentionally left in place or rolled back, with the change documented in your CMDB.

Frequently asked questions

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

Is CVE-2019-11708 being exploited right now?

Yes. CVE-2019-11708 is in the CISA Known Exploited Vulnerabilities catalog, added 2022-05-23. CISA only lists CVEs with confirmed active exploitation.

What is the CVSS score for CVE-2019-11708?

CVSS 10 (Critical). Use it together with your exposure picture (internet-facing first, then DMZ, then internal) when you set the patch order.

Can I run the fix without downtime?

It depends on the platform. Network appliances often support hitless HA upgrades (upgrade the standby, fail over, upgrade the former primary). Application servers usually need a service restart. Clustered services (Elasticsearch, Tomcat behind a load balancer, MySQL replicas) tolerate a rolling upgrade. Schedule a maintenance window if HA is not in place.

What if my version is not in the affected list?

Re-check the build string in the vendor advisory linked below. CVE records reflect the affected-products list at publication. Variants discovered later are added to the same advisory or a follow-up CVE.

References

*This guide was assembled from the official vendor advisory, NVD record, and CISA KEV listing on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*