How to Fix CVE-2026-3780: Foxit PDF Editor/Reader Installer Uncontrolled Search Path Privilege Escalation

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*By Sai Kiran Pandrala*

Last verified: 2026-05-25

CVE-2026-3780 is a foxit pdf editor/reader installer uncontrolled search path privilege escalation in Foxit Software Inc. Foxit PDF Reader. The fix is to upgrade to see vendor advisory and apply the runnable commands below.

What is CVE-2026-3780?

The application's installer runs with elevated privileges but resolves system executables and DLLs using untrusted search paths that can include user-writable directories, allowing a local attacker to place malicious binaries with the same names and have them loaded or executed instead of the legitimate system files, resulting in local privilege escalation.

In practical terms, a successful attacker gets elevation of privilege to administrator or root on the affected host. There is no confirmed in-the-wild exploitation listed in CISA's KEV catalog at the time of writing, but the CVSS rating still warrants prompt patching.

Am I affected?

You are affected if you run Foxit Software Inc. Foxit PDF Reader at a version listed in the Affected row above. Probe your installed build with the commands below.

# Confirm the installed version via your package manager
dpkg -l | grep -i foxit   # Debian/Ubuntu
rpm -qa | grep -i foxit   # RHEL/CentOS/Rocky

How to fix CVE-2026-3780

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.

Linux (Ubuntu / Debian)

# Vendor advisory: https://www.foxit.com/support/security-bulletins.html
sudo apt-get update
sudo apt-get install --only-upgrade foxit-pdf-reader
# Confirm the installed version meets or exceeds <patched-version>
dpkg -s foxit-pdf-reader | grep ^Version

Linux (RHEL / CentOS / Rocky)

sudo dnf upgrade --security foxit-pdf-reader -y
rpm -q foxit-pdf-reader

Windows (PowerShell, admin)

# Vendor advisory: https://www.foxit.com/support/security-bulletins.html
winget upgrade --id 'FoxitSoftwareInc.FoxitPDFReader' --silent --accept-source-agreements --accept-package-agreements
# If winget doesn't know the product, download the patched installer from the vendor and:
Start-Process -FilePath "$env:TEMP\FoxitPDFReader-<patched-version>.msi" -ArgumentList '/qn /norestart' -Wait

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

# Vendor advisory: https://www.foxit.com/support/security-bulletins.html
# Run as Administrator
$ErrorActionPreference = 'Stop'
$log = "$env:ProgramData\FoxitPDFReader-Patch-CVE-2026-3780.log"
function Write-Log($msg) { "$(Get-Date -Format s)  $msg" | Tee-Object -FilePath $log -Append }

Write-Log "Starting CVE-2026-3780 remediation for Foxit Software Inc. Foxit PDF Reader"

# 1. Detect: replace the path/version probe with one valid for your install
$installed = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*Foxit*' } |
    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\FoxitPDFReader-Backup-$(Get-Date -Format yyyyMMdd-HHmm)"
New-Item -ItemType Directory -Path $backup -Force | Out-Null
$src = "$env:ProgramFiles\Foxit Software Inc.\Foxit PDF Reader"
if (Test-Path $src) { Copy-Item -Path $src -Destination $backup -Recurse -Force }
Write-Log "Backed up config to $backup"

# 3. Apply the patched installer
$installer = "$env:TEMP\FoxitPDFReader-<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 { $_.Name -like '*Foxit*' } |
    Select-Object -First 1 -ExpandProperty Version)
if ([version]$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://www.foxit.com/support/security-bulletins.html
#!/usr/bin/env bash
set -euo pipefail
LOG=/var/log/foxit-pdf-reader-patch-cve-2026-3780.log
log()  { echo "$(date -Iseconds)  $*" | tee -a "$LOG"; }

log "Starting CVE-2026-3780 remediation for Foxit Software Inc. Foxit PDF Reader"

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

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

# 4. Verify
if [ "$PKG_MGR" = apt ]; then
    NEW=$(dpkg-query -W -f='${Version}' foxit-pdf-reader)
else
    NEW=$(rpm -q --queryformat '%{VERSION}' foxit-pdf-reader)
fi
log "After upgrade: $NEW"
log "Done. Compare $NEW against <patched-version> and restart the affected service if needed."

If you cannot patch immediately

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

No official vendor workaround is published for this CVE; patching is the documented fix. The runnable hardening below is generic defense in depth, not a substitute for the patch.

Restrict the affected service to trusted networks (Linux):

# Vendor advisory: https://www.foxit.com/support/security-bulletins.html
sudo iptables -A INPUT -p tcp --dport <port> -s 10.0.0.0/24 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport <port> -j DROP

Windows Firewall equivalent:

# Vendor advisory: https://www.foxit.com/support/security-bulletins.html
New-NetFirewallRule -DisplayName 'Allow affected service from admin subnet' -Direction Inbound -Action Allow -Protocol TCP -LocalPort <port> -RemoteAddress 10.0.0.0/24
New-NetFirewallRule -DisplayName 'Block affected service from everywhere else' -Direction Inbound -Action Block -Protocol TCP -LocalPort <port>

How to verify the fix worked

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

dpkg -l | grep -i "foxit"   # Debian/Ubuntu
rpm -qa | grep -i "foxit"   # RHEL/CentOS/Rocky

Expected output: the package version should meet or exceed the patched build.

Re-run any vulnerability scanner you used previously and confirm the finding for CVE-2026-3780 has cleared. Sweep your logs for 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-2026-3780 being actively exploited?

Not at the time of writing. It is not listed in CISA's Known Exploited Vulnerabilities catalog. That status can change, so monitor the vendor advisory and the KEV catalog if the system is exposed.

How severe is CVE-2026-3780?

CVSS rates it 7.3 (High). Use that score to set your patch priority alongside the other items in your queue.

Do I have to take Foxit PDF Reader 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-2026-3780 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

• Official vendor advisory: https://www.foxit.com/support/security-bulletins.html
• NVD entry: https://nvd.nist.gov/vuln/detail/CVE-2026-3780
• CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

*Written by Sai Kiran Pandrala. Last verified 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.*