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CVE-2026-15341 — The User Session Synchronizer plugin for WordPress is vulnerable to Authentication Bypass…

Key facts

CVE-2026-15341 is a Critical (9.8) vulnerability: The User Session Synchronizer plugin for WordPress is vulnerable to Authentication Bypass…. This entry ships a detection-only PoC and a Docker test lab.
CVE CVE-2026-15341
Severity Critical (9.8)
Detection / prevention —
PoC poc.py
Source 2026/CVE-2026-15341/

Details

English | 한국어

Description

The User Session Synchronizer plugin for WordPress is vulnerable to Authentication Bypass leading to Account Takeover in all versions up to, and including, 1.4.0. The synchronize_session() function, hooked on init and therefore executed on every request, performs no nonce, capability, or shared-secret validation against the attacker-supplied ussync-key, ussync-token, and ussync-ref parameters; when ussync-key references an unregistered slot, get_option() returns false for both the secret key and the domain list, causing the AES-256-CBC encryption key to degrade to the fully predictable md5('') and the referer allowlist to collapse to an empty-string match, while the AES IV is unconditionally hard-coded as md5('another-secret'). This makes it possible for unauthenticated attackers to supply a crafted request encrypting any known or guessable user email address in the ussync-ref parameter, causing the handler to call wp_set_auth_cookie() for the matched user and granting full authentication as that user — including administrators — with no prior knowledge of site secrets.

Vulnerability Details

Property Value
CVE ID CVE-2026-15341
CVSS Score 9.8

Proof of Concept

Download

# Download PoC script
curl -O https://raw.githubusercontent.com/fankh/vulnerability-poc/main/2026/CVE-2026-15341/poc.py

Usage

# Run PoC against target
python3 poc.py --target <TARGET_URL>

# With authentication
python3 poc.py --target <TARGET_URL> --username <USER> --password <PASS>

⚠️ Warning: This PoC is for authorized security testing only. It uses detection-only techniques and does not exploit or damage target systems.

Test Lab

This repository includes a Docker-based test environment with both vulnerable and patched applications.

Quick Start

# Clone and navigate to CVE directory
cd CVE-2026-15341

# Start both applications
docker-compose up -d

# Run tests
./run-tests.sh    # Linux/Mac
./run-tests.ps1   # Windows PowerShell

Application Endpoints

Application URL Status
Vulnerable App http://localhost:8080 Shows vulnerability
Patched App http://localhost:8081 Demonstrates fix

Directory Structure

├── README.md           # English documentation
├── README_KO.md        # Korean documentation
├── poc.py              # PoC detection script
├── docker-compose.yml  # Container orchestration
├── run-tests.sh        # Linux/Mac test runner
├── run-tests.ps1       # Windows test runner
├── vulnerable-app/     # Vulnerable version
│   ├── app.py
│   ├── Dockerfile
│   └── requirements.txt
└── patched-app/        # Fixed version
    ├── app.py
    ├── Dockerfile
    └── requirements.txt

References

  • https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L117
  • https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L286
  • https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L310
  • https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L422
  • https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L598
  • https://plugins.trac.wordpress.org/browser/user-session-synchronizer/tags/1.4.0/includes/class-user-session-synchronizer.php#L631
  • https://www.wordfence.com/threat-intel/vulnerabilities/id/cbc32e6d-47c5-4050-ba77-5a54203fe56a?source=cve

Generated by PoC Generator on 2026-08-15T19:36:41.858208846

Frequently asked questions

What is CVE-2026-15341?

CVE-2026-15341 is a Critical (9.8) vulnerability: The User Session Synchronizer plugin for WordPress is vulnerable to Authentication Bypass…. This entry ships a detection-only PoC and a Docker test lab.

How do I detect CVE-2026-15341?

Run the detection-only PoC included with this entry against your Docker test lab to confirm whether a target is affected; pair it with your own IDS logging.

How do I block or mitigate CVE-2026-15341?

Upgrade to a fixed version per the vendor advisory; the NVD record lists the affected versions. Use the included PoC to verify your remediation.

For authorized security testing and research only. See the full source and NVD record.