● High · CVSS 8.5

How to Fix CVE-2026-40031: MemProcFS < 5.17 DLL/Shared Library Hijacking in MemProcFS

Q: Is CVE-2026-40031 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.

Q: How severe is CVE-2026-40031?

CVSS rates it 8.5 (High). Use that score to set your patch priority alongside the other items in your queue.

Q: Do I have to take MemProcFS 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.

Q: What if my vulnerability scanner still flags CVE-2026-40031 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.

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*By Sai Kiran Pandrala*

Last verified: 2026-05-25

⚡ At a glance


Severity	CVSS 8.5, High
Actively exploited?	No
Affected	Ufrisk MemProcFS (0 <= 5.16.12)
Fixed in	See vendor advisory
Type (CWE)	CWE-427: Uncontrolled Search Path Element

CVE-2026-40031 is a memprocfs < 5.17 dll/shared library hijacking in Ufrisk MemProcFS. The fix is to upgrade to see vendor advisory and apply the runnable commands below.

What is CVE-2026-40031?

MemProcFS before 5.17 contains multiple unsafe library-loading patterns that enable DLL and shared-library hijacking across six attack surfaces, including bare-name LoadLibraryU and dlopen calls without path qualification for vmmpyc, libMSCompression, and plugin DLLs. An attacker who places a malicious DLL or shared library in the working directory or manipulates LD_LIBRARY_PATH can achieve arbitrary code execution when MemProcFS loads.

In practical terms, a successful attacker gets remote code execution on the affected system. 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 Ufrisk MemProcFS 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 memprocfs   # Debian/Ubuntu
rpm -qa | grep -i memprocfs   # RHEL/CentOS/Rocky

How to fix CVE-2026-40031

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://github.com/ufrisk/MemProcFS/releases/tag/v5.17
sudo apt-get update
sudo apt-get install --only-upgrade memprocfs
# Confirm the installed version meets or exceeds <patched-version>
dpkg -s memprocfs | grep ^Version

Linux (RHEL / CentOS / Rocky)


sudo dnf upgrade --security memprocfs -y
rpm -q memprocfs

Windows (PowerShell, admin)


# Vendor advisory: https://github.com/ufrisk/MemProcFS/releases/tag/v5.17
winget upgrade --id 'Ufrisk.MemProcFS' --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\MemProcFS-<patched-version>.msi" -ArgumentList '/qn /norestart' -Wait

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


# Vendor advisory: https://github.com/ufrisk/MemProcFS/releases/tag/v5.17
# Run as Administrator
$ErrorActionPreference = 'Stop'
$log = "$env:ProgramData\MemProcFS-Patch-CVE-2026-40031.log"
function Write-Log($msg) { "$(Get-Date -Format s)  $msg" | Tee-Object -FilePath $log -Append }

Write-Log "Starting CVE-2026-40031 remediation for Ufrisk MemProcFS"

# 1. Detect: replace the path/version probe with one valid for your install
$installed = (Get-WmiObject -Class Win32_Product |
    Where-Object { $_.Name -like '*MemProcFS*' } |
    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\MemProcFS-Backup-$(Get-Date -Format yyyyMMdd-HHmm)"
New-Item -ItemType Directory -Path $backup -Force | Out-Null
$src = "$env:ProgramFiles\Ufrisk\MemProcFS"
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\MemProcFS-<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 { $_.Name -like '*MemProcFS*' } |
    Select-Object -First 1 -ExpandProperty Version)
if ([version]$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://github.com/ufrisk/MemProcFS/releases/tag/v5.17
#!/usr/bin/env bash
set -euo pipefail
LOG=/var/log/memprocfs-patch-cve-2026-40031.log
log()  { echo "$(date -Iseconds)  $*" | tee -a "$LOG"; }

log "Starting CVE-2026-40031 remediation for Ufrisk MemProcFS"

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

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

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

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.


dpkg -l | grep -i "memprocfs"   # Debian/Ubuntu
rpm -qa | grep -i "memprocfs"   # 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-2026-40031 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-2026-40031 being actively exploited?