How to Fix CVE-2026-27947: Improper neutralization of argument delimiters in a command ('argument injection') in groupoffice

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

CVE-2026-27947 is a improper neutralization of argument delimiters in a command ('argument injection') in Intermesh groupoffice. The fix is to apply the vendor patch noted below.

What is CVE-2026-27947?

Group-Office is an enterprise customer relationship management and groupware tool. Versions prior to 26.0.9, 25.0.87, and 6.8.154 have an authenticated Remote Code Execution vulnerability in the TNEF attachment processing flow. The vulnerable path extracts attacker-controlled files from winmail.dat and then invokes zip with a shell wildcard (*). Because extracted filenames are attacker-controlled, they can be interpreted as zip options and lead to arbitrary command execution. Versions 26.0.9, 25.0.87, and 6.8.154 fix the issue. The CVSS base score is 9.4 (Critical), which puts this in the upper risk band and warrants a fast patch cycle. The official advisory is at https://github.com/Intermesh/groupoffice/security/advisories/GHSA-2rwh-9qp7-f92x.

Am I affected?

Check the version of groupoffice you are running and compare it against the Affected row above (groupoffice >= 26.0.0, < 26.0.9; groupoffice >= 25.0.0, < 25.0.87; groupoffice < 6.8.154). If your build sits inside the affected range, you must patch.

Run the version check that fits your platform:

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

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

How to fix CVE-2026-27947

Upgrade groupoffice 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 groupoffice
dpkg -s groupoffice | grep -i ^Version

RHEL / CentOS / Rocky / AlmaLinux

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

SUSE / openSUSE

sudo zypper refresh
sudo zypper update groupoffice
rpm -q groupoffice

Complete PowerShell remediation script (Windows)

# Fix script for CVE-2026-27947 affecting groupoffice
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-27947-fix-$(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"
    $pkg = Get-Package -Name "*groupoffice*" -ErrorAction SilentlyContinue
    if ($pkg) { $pkg | Format-Table Name, Version }
    else { Write-Host "Not detected via Get-Package; try winget list" }

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

    Write-Host "[3/4] Apply the upgrade to See vendor advisory"
    winget upgrade --name "groupoffice" --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 "groupoffice"
    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-2026-27947 affecting groupoffice
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-27947-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 groupoffice 2>/dev/null | grep -i ^Version || echo "groupoffice not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q groupoffice || echo "groupoffice not installed via rpm"
fi

echo "[2/4] Backup configuration"
BACKUP="/root/backup-cve-2026-27947-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/groupoffice /etc/groupoffice.d /etc/groupoffice.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 groupoffice
elif command -v dnf >/dev/null; then
    dnf upgrade --refresh -y groupoffice
elif command -v yum >/dev/null; then
    yum update -y groupoffice
elif command -v zypper >/dev/null; then
    zypper --non-interactive update groupoffice
fi

echo "[4/4] Verify the patched build"
if command -v dpkg >/dev/null; then
    dpkg -s groupoffice 2>/dev/null | grep -i ^Version
elif command -v rpm >/dev/null; then
    rpm -q groupoffice
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-2026-27947" -Direction Inbound -Action Block -Protocol TCP -LocalPort 80,443 -RemoteAddress Any -Enabled True
Get-NetFirewallRule -DisplayName "Block-CVE-2026-27947"

Disable the affected service (Linux)

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

Related fixes

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

• How to Fix CVE-2026-33238: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal') — CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
• How to Fix CVE-2026-42373: Use of Hard-coded Credentials in DIR-605L Firmware — Use of Hard-coded Credentials in DIR-605L Firmware
• How to Fix CVE-2026-35479: InvenTree (Bundle Sibling) , InvenTree (Bundle Sibling)
• How to Fix CVE-2026-31816: Budibase Universal Auth Bypass via Webhook Query Param Injection , Budibase Universal Auth Bypass via Webhook Query Param Injection
• How to Fix CVE-2026-25727: Stack Buffer Overflow in time , Stack Buffer Overflow in time

Is CVE-2026-27947 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-2026-27947?

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-2026-27947?

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

Where is the official advisory for CVE-2026-27947?

The vendor advisory is at https://github.com/Intermesh/groupoffice/security/advisories/GHSA-2rwh-9qp7-f92x. The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-27947.

References

• Official vendor advisory: https://github.com/Intermesh/groupoffice/security/advisories/GHSA-2rwh-9qp7-f92x
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27947
• CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog

*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.*