How to Fix CVE-2026-27904: Regex denial of service in minimatch

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

CVE-2026-27904 is a regex denial of service in isaacs minimatch. The fix is to apply the vendor patch noted below.

What is CVE-2026-27904?

minimatch is a minimal matching utility for converting glob expressions into JavaScript RegExp objects. Prior to version 10.2.3, 9.0.7, 8.0.6, 7.4.8, 6.2.2, 5.1.8, 4.2.5, and 3.1.4, nested *() extglobs produce regexps with nested unbounded quantifiers (e.g. (?:(?:a|b)*)*), which exhibit catastrophic backtracking in V8. With a 12-byte pattern *(*(*(a|b))) and an 18-byte non-matching input, minimatch() stalls for over 7 seconds. Adding a single nesting level or a few input characters pushes this to minutes. This is the most severe finding: it is triggered by the default minimatch() API with no special options, and the minimum viable pattern is only 12 bytes. The same issue affects +() extglobs equally. Versions 10.2.3, 9.0.7, 8.0.6, 7.4.8, 6.2.2, 5.1.8, 4.2.5, and 3.1.4 fix the issue. The CVSS base score is 7.5 (High), which puts this in the upper risk band and warrants a fast patch cycle. The official advisory is at https://github.com/isaacs/minimatch/security/advisories/GHSA-23c5-xmqv-rm74.

Am I affected?

Check the version of minimatch you are running and compare it against the Affected row above (minimatch >= 10.0.0, < 10.2.3; minimatch >= 9.0.0, < 9.0.7; minimatch >= 8.0.0, < 8.0.6; minimatch >= 7.0.0, < 7.4.8; minimatch >= 6.0.0, < 6.2.2; minimatch >= 5.0.0, < 5.1.8). If your build sits inside the affected range, you must patch.

Run the version check that fits your platform:

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

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

How to fix CVE-2026-27904

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

RHEL / CentOS / Rocky / AlmaLinux

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

SUSE / openSUSE

sudo zypper refresh
sudo zypper update minimatch
rpm -q minimatch

Complete PowerShell remediation script (Windows)

# Fix script for CVE-2026-27904 affecting minimatch
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-27904-fix-$(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"
    $pkg = Get-Package -Name "*minimatch*" -ErrorAction SilentlyContinue
    if ($pkg) { $pkg | Format-Table Name, Version }
    else { Write-Host "Not detected via Get-Package; try winget list" }

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

    Write-Host "[3/4] Apply the upgrade to See vendor advisory"
    winget upgrade --name "minimatch" --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 "minimatch"
    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-2026-27904 affecting minimatch
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-27904-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 minimatch 2>/dev/null | grep -i ^Version || echo "minimatch not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q minimatch || echo "minimatch not installed via rpm"
fi

echo "[2/4] Backup configuration"
BACKUP="/root/backup-cve-2026-27904-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/minimatch /etc/minimatch.d /etc/minimatch.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 minimatch
elif command -v dnf >/dev/null; then
    dnf upgrade --refresh -y minimatch
elif command -v yum >/dev/null; then
    yum update -y minimatch
elif command -v zypper >/dev/null; then
    zypper --non-interactive update minimatch
fi

echo "[4/4] Verify the patched build"
if command -v dpkg >/dev/null; then
    dpkg -s minimatch 2>/dev/null | grep -i ^Version
elif command -v rpm >/dev/null; then
    rpm -q minimatch
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-2026-27904" -Direction Inbound -Action Block -Protocol TCP -LocalPort 80,443 -RemoteAddress Any -Enabled True
Get-NetFirewallRule -DisplayName "Block-CVE-2026-27904"

Disable the affected service (Linux)

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

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Is CVE-2026-27904 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-2026-27904?

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-2026-27904?

7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

Where is the official advisory for CVE-2026-27904?

The vendor advisory is at https://github.com/isaacs/minimatch/security/advisories/GHSA-23c5-xmqv-rm74. The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-27904.

References

• Official vendor advisory: https://github.com/isaacs/minimatch/security/advisories/GHSA-23c5-xmqv-rm74
• NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-27904
• 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.*