● High · CVSS 8.9

How to Fix CVE-2026-27727: Improper neutralization of special elements in output used by a downstream component ('injection') in mchange-commons-java

Q: What is the CVSS score for CVE-2026-27727?

8.9 (High). Vector: `CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H`.

Q: Where is the official advisory for CVE-2026-27727?

The vendor advisory is at [https://github.com/swaldman/mchange-commons-java/security/advisories/GHSA-m2cm-222f-qw44](https://github.com/swaldman/mchange-commons-java/security/advisories/GHSA-m2cm-222f-qw44). The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-27727.

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

CVE-2026-27727 is a improper neutralization of special elements in output used by a downstream component ('injection') in swaldman mchange-commons-java. The fix is to apply the vendor patch noted below.

⚡ At a glance


Severity	8.9 (High)
Actively exploited?	No public listing in CISA KEV
Affected	mchange-commons-java < 0.4.0
Fixed in	See vendor advisory
Type (CWE)	CWE-74: Improper Neutralization of Special Elements in Output Used by a Downstream Component ('Injection')

What is CVE-2026-27727?

mchange-commons-java, a library that provides Java utilities, includes code that mirrors early implementations of JNDI functionality, including support for remote factoryClassLocation values, by which code can be downloaded and invoked within a running application. If an attacker can provoke an application to read a maliciously crafted jaxax.naming.Reference or serialized object, they can provoke the download and execution of malicious code. Implementations of this functionality within the JDK were disabled by default behind a System property that defaults to false, com.sun.jndi.ldap.object.trustURLCodebase. However, since mchange-commons-java includes an independent implementation of JNDI derefencing, libraries (such as c3p0) that resolve references via that implementation could be provoked to download and execute malicious code even after the JDK was hardened. Mirroring the JDK patch, mchange-commons-java's JNDI functionality is gated by configuration parameters that default to restrictive values starting in version 0.4.0. No known workarounds are available. Versions prior to 0.4.0 should be avoided on application CLASSPATHs. The CVSS base score is 8.9 (High), which puts this in the upper risk band and warrants a fast patch cycle. The official advisory is at https://github.com/swaldman/mchange-commons-java/security/advisories/GHSA-m2cm-222f-qw44.

Am I affected?

Check the version of mchange-commons-java you are running and compare it against the Affected row above (mchange-commons-java < 0.4.0). If your build sits inside the affected range, you must patch.

Run the version check that fits your platform:


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


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

How to fix CVE-2026-27727

Upgrade mchange-commons-java 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 mchange-commons-java
dpkg -s mchange-commons-java | grep -i ^Version

RHEL / CentOS / Rocky / AlmaLinux


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

SUSE / openSUSE


sudo zypper refresh
sudo zypper update mchange-commons-java
rpm -q mchange-commons-java

Complete PowerShell remediation script (Windows)


# Fix script for CVE-2026-27727 affecting mchange-commons-java
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-27727-fix-$(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"
    $pkg = Get-Package -Name "*mchange-commons-java*" -ErrorAction SilentlyContinue
    if ($pkg) { $pkg | Format-Table Name, Version }
    else { Write-Host "Not detected via Get-Package; try winget list" }

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

    Write-Host "[3/4] Apply the upgrade to See vendor advisory"
    winget upgrade --name "mchange-commons-java" --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 "mchange-commons-java"
    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-2026-27727 affecting mchange-commons-java
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-27727-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 mchange-commons-java 2>/dev/null | grep -i ^Version || echo "mchange-commons-java not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q mchange-commons-java || echo "mchange-commons-java not installed via rpm"
fi

echo "[2/4] Backup configuration"
BACKUP="/root/backup-cve-2026-27727-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/mchange-commons-java /etc/mchange-commons-java.d /etc/mchange-commons-java.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 mchange-commons-java
elif command -v dnf >/dev/null; then
    dnf upgrade --refresh -y mchange-commons-java
elif command -v yum >/dev/null; then
    yum update -y mchange-commons-java
elif command -v zypper >/dev/null; then
    zypper --non-interactive update mchange-commons-java
fi

echo "[4/4] Verify the patched build"
if command -v dpkg >/dev/null; then
    dpkg -s mchange-commons-java 2>/dev/null | grep -i ^Version
elif command -v rpm >/dev/null; then
    rpm -q mchange-commons-java
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-2026-27727" -Direction Inbound -Action Block -Protocol TCP -LocalPort 80,443 -RemoteAddress Any -Enabled True
Get-NetFirewallRule -DisplayName "Block-CVE-2026-27727"

Disable the affected service (Linux)


sudo systemctl stop mchange-commons-java 2>/dev/null || true
sudo systemctl disable mchange-commons-java 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 mchange-commons-java 2>/dev/null | grep -i ^Version
rpm -q mchange-commons-java 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 "*mchange-commons-java*" | 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

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Is CVE-2026-27727 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-2026-27727?

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-2026-27727?

8.9 (High). Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:H/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H.

Where is the official advisory for CVE-2026-27727?

The vendor advisory is at https://github.com/swaldman/mchange-commons-java/security/advisories/GHSA-m2cm-222f-qw44. The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-27727.

References

Official vendor advisory: https://github.com/swaldman/mchange-commons-java/security/advisories/GHSA-m2cm-222f-qw44
NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27727
CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Additional reference: https://mogwailabs.de/en/blog/2025/02/c3p0-you-little-rascal
Additional reference: https://www.mchange.com/projects/c3p0/#configuring_security
Additional reference: https://www.mchange.com/projects/c3p0/#security-note

*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.*