● High · CVSS 8.1

How to Fix CVE-2026-1321: Missing authorization in Membership Plugin – Restrict Content

Q: What is the CVSS score for CVE-2026-1321?

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

Q: Where is the official advisory for CVE-2026-1321?

The vendor advisory is at [https://www.wordfence.com/threat-intel/vulnerabilities/id/abfaa4a6-92b0-4233-b08d-e668090d3fc2?source=cve](https://www.wordfence.com/threat-intel/vulnerabilities/id/abfaa4a6-92b0-4233-b08d-e668090d3fc2?source=cve). The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-1321.

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

CVE-2026-1321 is a missing authorization in stellarwp Membership Plugin – Restrict Content. The fix is to apply the vendor patch noted below.

⚡ At a glance


Severity	8.1 (High)
Actively exploited?	No public listing in CISA KEV
Affected	Membership Plugin – Restrict Content 0 to <=3.2.20
Fixed in	See vendor advisory
Type (CWE)	CWE-862 Missing Authorization

What is CVE-2026-1321?

The Membership Plugin – Restrict Content plugin for WordPress is vulnerable to Privilege Escalation in all versions up to, and including, 3.2.20. This is due to the rcp_setup_registration_init() function accepting any membership level ID via the rcp_level POST parameter without validating that the level is active or that payment is required. Combined with the add_user_role() method which assigns the WordPress role configured on the membership level without status checks, this makes it possible for unauthenticated attackers to register with any membership level, including inactive levels that grant privileged WordPress roles such as Administrator, or paid levels that charge a sign-up fee. The vulnerability was partially patched in version 3.2.18. The CVSS base score is 8.1 (High), which puts this in the upper risk band and warrants a fast patch cycle. The official advisory is at https://www.wordfence.com/threat-intel/vulnerabilities/id/abfaa4a6-92b0-4233-b08d-e668090d3fc2?source=cve.

Am I affected?

Check the version of Membership Plugin – Restrict Content you are running and compare it against the Affected row above (Membership Plugin – Restrict Content 0 to <=3.2.20). If your build sits inside the affected range, you must patch.

Run the version check that fits your platform:


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


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

How to fix CVE-2026-1321

Upgrade Membership Plugin – Restrict Content 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 membership-plugin-restrict-content
dpkg -s membership-plugin-restrict-content | grep -i ^Version

RHEL / CentOS / Rocky / AlmaLinux


sudo dnf upgrade --refresh membership-plugin-restrict-content -y
# or for older releases:
sudo yum update membership-plugin-restrict-content -y
rpm -q membership-plugin-restrict-content

SUSE / openSUSE


sudo zypper refresh
sudo zypper update membership-plugin-restrict-content
rpm -q membership-plugin-restrict-content

PHP / Composer


composer update stellarwp/membership-plugin-restrict-content 2>/dev/null || composer update
composer show | head -20

WordPress


# Update via WP-CLI
wp plugin update --all
wp core update

Complete PowerShell remediation script (Windows)


# Fix script for CVE-2026-1321 affecting Membership Plugin – Restrict Content
# Run as administrator. Detect -> backup -> upgrade -> verify -> log.

$ErrorActionPreference = "Stop"
$LogPath  = "C:\Logs\CVE-2026-1321-fix-$(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"
    $pkg = Get-Package -Name "*Membership Plugin – Restrict Content*" -ErrorAction SilentlyContinue
    if ($pkg) { $pkg | Format-Table Name, Version }
    else { Write-Host "Not detected via Get-Package; try winget list" }

    Write-Host "[2/4] Backup configuration"
    $backup = "C:\Backup\membership-plugin-restrict-content-$(Get-Date -Format yyyyMMdd)"
    New-Item -ItemType Directory -Force $backup | Out-Null
    Get-ChildItem "C:\ProgramData\Membership Plugin – Restrict Content" -ErrorAction SilentlyContinue |
        Copy-Item -Destination $backup -Recurse -Force -ErrorAction SilentlyContinue

    Write-Host "[3/4] Apply the upgrade to See vendor advisory"
    winget upgrade --name "Membership Plugin – Restrict Content" --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 "Membership Plugin – Restrict Content"
    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-2026-1321 affecting Membership Plugin – Restrict Content
# Detect -> backup -> upgrade -> verify -> log.

set -euo pipefail
LOG="/var/log/cve-2026-1321-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 membership-plugin-restrict-content 2>/dev/null | grep -i ^Version || echo "membership-plugin-restrict-content not installed via dpkg"
elif command -v rpm >/dev/null; then
    rpm -q membership-plugin-restrict-content || echo "membership-plugin-restrict-content not installed via rpm"
fi

echo "[2/4] Backup configuration"
BACKUP="/root/backup-cve-2026-1321-$(date +%Y%m%d)"
mkdir -p "$BACKUP"
for d in /etc/membership-plugin-restrict-content /etc/membership-plugin-restrict-content.d /etc/membership-plugin-restrict-content.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 membership-plugin-restrict-content
elif command -v dnf >/dev/null; then
    dnf upgrade --refresh -y membership-plugin-restrict-content
elif command -v yum >/dev/null; then
    yum update -y membership-plugin-restrict-content
elif command -v zypper >/dev/null; then
    zypper --non-interactive update membership-plugin-restrict-content
fi

echo "[4/4] Verify the patched build"
if command -v dpkg >/dev/null; then
    dpkg -s membership-plugin-restrict-content 2>/dev/null | grep -i ^Version
elif command -v rpm >/dev/null; then
    rpm -q membership-plugin-restrict-content
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-2026-1321" -Direction Inbound -Action Block -Protocol TCP -LocalPort 80,443 -RemoteAddress Any -Enabled True
Get-NetFirewallRule -DisplayName "Block-CVE-2026-1321"

Disable the affected service (Linux)


sudo systemctl stop membership-plugin-restrict-content 2>/dev/null || true
sudo systemctl disable membership-plugin-restrict-content 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 membership-plugin-restrict-content 2>/dev/null | grep -i ^Version
rpm -q membership-plugin-restrict-content 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 "*Membership Plugin – Restrict Content*" | 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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Is CVE-2026-1321 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-2026-1321?

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-2026-1321?

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

Where is the official advisory for CVE-2026-1321?

The vendor advisory is at https://www.wordfence.com/threat-intel/vulnerabilities/id/abfaa4a6-92b0-4233-b08d-e668090d3fc2?source=cve. The NVD record is at https://nvd.nist.gov/vuln/detail/CVE-2026-1321.

References

Official vendor advisory: https://www.wordfence.com/threat-intel/vulnerabilities/id/abfaa4a6-92b0-4233-b08d-e668090d3fc2?source=cve
NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-1321
CISA KEV catalog: https://www.cisa.gov/known-exploited-vulnerabilities-catalog
Additional reference: https://plugins.trac.wordpress.org/browser/restrict-content/tags/3.2.15/core/includes/registration-functions.php#L1191
Additional reference: https://plugins.trac.wordpress.org/browser/restrict-content/tags/3.2.15/core/includes/registration-functions.php#L1203
Additional reference: https://plugins.trac.wordpress.org/browser/restrict-content/tags/3.2.15/core/includes/class-rcp-registration.php#L107

*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.*