● Medium · CVSS 4.8

How to Fix CVE-2026-3389: Null pointer dereference in Squirrel

Q: What is the CVSS score for CVE-2026-3389?

4.8 (Medium). Vector: `CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P`.

Q: Where is the official advisory for CVE-2026-3389?

The vendor advisory is at [https://vuldb.com/?id.348275](https://vuldb.com/?id.348275). The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-3389.

By Sai Kiran Pandrala. Last verified: 2026-05-25.

CVE-2026-3389 is a null pointer dereference in n/a Squirrel. The fix is to apply the vendor patch noted below.

⚡ At a glance


Severity	4.8 (Medium)
Actively exploited?	No public listing in CISA KEV
Affected	Squirrel 3.0; Squirrel 3.1; Squirrel 3.2
Fixed in	See vendor advisory
Type (CWE)	CWE-476: NULL Pointer Dereference

What is CVE-2026-3389?

A vulnerability was determined in Squirrel up to 3.2. This vulnerability affects the function sqstd_rex_newnode in the library sqstdlib/sqstdrex.cpp. Executing a manipulation can lead to null pointer dereference. The attack can only be executed locally. The exploit has been publicly disclosed and may be utilized. The project was informed of the problem early through an issue report but has not responded yet. The CVSS base score is 4.8 (Medium). The official advisory is at https://vuldb.com/?id.348275.

Am I affected?

Check the version of Squirrel you are running and compare it against the Affected row above (Squirrel 3.0; Squirrel 3.1; Squirrel 3.2). If your build sits inside the affected range, you must patch.

Run the version check that fits your platform:


# Linux package check
dpkg -s squirrel 2>/dev/null | grep -i ^Version
rpm -q squirrel 2>/dev/null
command -v squirrel >/dev/null && squirrel --version 2>/dev/null


# Windows (PowerShell)
Get-Package -Name "*Squirrel*" -ErrorAction SilentlyContinue | Select-Object Name, Version
winget list --name "Squirrel" 2>$null

How to fix CVE-2026-3389

Upgrade Squirrel to a patched build: See vendor advisory. The vendor advisory is the source of truth for the exact fixed version.

Ubuntu / Debian


sudo apt-get update
sudo apt-get install --only-upgrade squirrel
dpkg -s squirrel | grep -i ^Version

RHEL / CentOS / Rocky / AlmaLinux


sudo dnf upgrade --refresh squirrel -y
# or for older releases:
sudo yum update squirrel -y
rpm -q squirrel

SUSE / openSUSE


sudo zypper refresh
sudo zypper update squirrel
rpm -q squirrel

Node.js / npm


# Update the affected package in your project
npm install Squirrel@latest
npm ls Squirrel
npm audit fix

Complete PowerShell remediation script (Windows)


# Fix script for CVE-2026-3389 affecting Squirrel
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-3389-fix-$(Get-Date -Format yyyyMMdd-HHmmss).log"
New-Item -ItemType Directory -Force (Split-Path $LogPath) | Out-Null
Start-Transcript -Path $LogPath -Append

try {
    Write-Host "[1/4] Detect installed version"
    $pkg = Get-Package -Name "*Squirrel*" -ErrorAction SilentlyContinue
    if ($pkg) { $pkg | Format-Table Name, Version }
    else { Write-Host "Not detected via Get-Package; try winget list" }

    Write-Host "[2/4] Backup configuration"
    $backup = "C:\Backup\squirrel-$(Get-Date -Format yyyyMMdd)"
    New-Item -ItemType Directory -Force $backup | Out-Null
    Get-ChildItem "C:\ProgramData\Squirrel" -ErrorAction SilentlyContinue |
        Copy-Item -Destination $backup -Recurse -Force -ErrorAction SilentlyContinue

    Write-Host "[3/4] Apply the upgrade to See vendor advisory"
    winget upgrade --name "Squirrel" --silent --accept-source-agreements --accept-package-agreements
    if ($LASTEXITCODE -ne 0) {
        # Fallback: pull latest via OS update channel
        Install-Module -Name PSWindowsUpdate -Force -SkipPublisherCheck -ErrorAction SilentlyContinue
        Import-Module PSWindowsUpdate
        Install-WindowsUpdate -MicrosoftUpdate -AcceptAll -IgnoreReboot
    }

    Write-Host "[4/4] Verify the patched build"
    winget list --name "Squirrel"
    Write-Host "Patch applied. Reboot if prompted."
    exit 0
} catch {
    Write-Error "Patch failed: $_"
    exit 1
} finally {
    Stop-Transcript
}

Complete Bash remediation script (Linux)


#!/usr/bin/env bash
# Fix script for CVE-2026-3389 affecting Squirrel
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-3389-fix-$(date +%Y%m%d-%H%M%S).log"
exec > >(tee -a "$LOG") 2>&1

echo "[1/4] Detect installed version"
if command -v dpkg >/dev/null; then
    dpkg -s squirrel 2>/dev/null | grep -i ^Version || echo "squirrel not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q squirrel || echo "squirrel not installed via rpm"
fi

echo "[2/4] Backup configuration"
BACKUP="/root/backup-cve-2026-3389-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/squirrel /etc/squirrel.d /etc/squirrel.conf; do
    [ -e "$d" ] && cp -a "$d" "$BACKUP/" || true
done

echo "[3/4] Apply the upgrade (target: See vendor advisory)"
if command -v apt-get >/dev/null; then
    apt-get update
    apt-get install --only-upgrade -y squirrel
elif command -v dnf >/dev/null; then
    dnf upgrade --refresh -y squirrel
elif command -v yum >/dev/null; then
    yum update -y squirrel
elif command -v zypper >/dev/null; then
    zypper --non-interactive update squirrel
fi

echo "[4/4] Verify the patched build"
if command -v dpkg >/dev/null; then
    dpkg -s squirrel 2>/dev/null | grep -i ^Version
elif command -v rpm >/dev/null; then
    rpm -q squirrel
fi
echo "Done. Restart any service that loaded the old library."

If you can't patch immediately

Apply at least one of the following inline controls until you can deploy the patched build. None replace the upgrade.

Restrict exposure with nftables (Linux)


# Allow only trusted CIDR to reach the affected service ports
sudo nft add table inet filter 2>/dev/null || true
sudo nft 'add chain inet filter input { type filter hook input priority 0 ; }' 2>/dev/null || true
sudo nft 'add rule inet filter input tcp dport {80, 443} ip saddr != 10.0.0.0/8 drop'
sudo nft list ruleset

Block at the host firewall (Windows)


New-NetFirewallRule -DisplayName "Block-CVE-2026-3389" -Direction Inbound -Action Block -Protocol TCP -LocalPort 80,443 -RemoteAddress Any -Enabled True
Get-NetFirewallRule -DisplayName "Block-CVE-2026-3389"

Disable the affected service (Linux)


sudo systemctl stop squirrel 2>/dev/null || true
sudo systemctl disable squirrel 2>/dev/null || true

If the vendor advisory lists an official workaround, prefer that wording verbatim. If no workaround is published, the only safe remediation is the patch.

How to verify the fix worked

After upgrading, confirm the installed version matches the patched build and that no old library is still loaded by a long-running process.


# Linux
dpkg -s squirrel 2>/dev/null | grep -i ^Version
rpm -q squirrel 2>/dev/null || true
# Pid map check for old library handles
sudo lsof +c0 2>/dev/null | grep -i "DEL.*lib" || true


# Windows
Get-Package -Name "*Squirrel*" | Select-Object Name, Version
Get-HotFix | Sort-Object InstalledOn -Descending | Select-Object -First 5

Expected: the reported version is at or above See vendor advisory. Restart the affected service (systemctl restart <service> on Linux, or restart the Windows service) so it loads the patched binary.

Frequently asked questions

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

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How to Fix CVE-2026-30643: n/a (Bundle Sibling) — n/a (Bundle Sibling)
How to Fix CVE-2026-40574: Incorrect authorization in oauth2-proxy , Incorrect authorization in oauth2-proxy
How to Fix CVE-2026-40255: Cwe-601: url redirection to untrusted site in http-core , Cwe-601: url redirection to untrusted site in http-core
How to Fix CVE-2026-30947: Parse Server ha a bypass of class-level permissions in LiveQuery , Parse Server ha a bypass of class-level permissions in LiveQuery

Is CVE-2026-3389 actively exploited?

There is no public confirmation of exploitation in the wild listed in CISA KEV at the time of this writing. Patch anyway. Public exploits commonly follow disclosure within weeks.

Do I need to reboot after patching CVE-2026-3389?

For kernel and OS-level updates, yes. For most userland packages a systemctl restart <service> is enough on Linux, and restarting the Windows service or app on Windows. Any process that loaded the old library keeps using it until restarted.

What is the CVSS score for CVE-2026-3389?

4.8 (Medium). Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:P.

Where is the official advisory for CVE-2026-3389?

The vendor advisory is at https://vuldb.com/?id.348275. The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-3389.

References

Official vendor advisory: https://vuldb.com/?id.348275
NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-3389
CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Additional reference: https://vuldb.com/?ctiid.348275
Additional reference: https://vuldb.com/?submit.761315
Additional reference: https://github.com/albertodemichelis/squirrel/issues/314

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