CVE-2026-107508: Ultimate Multisite Path Traversal Flaw

CVE-2026-107508 Overview

CVE-2026-107508 is a Local File Inclusion (LFI) vulnerability in the Ultimate Multisite WordPress plugin before version 2.17.2. The plugin fails to validate a user-supplied value used to select a file for inclusion. Unauthenticated attackers can exploit this flaw to include and read arbitrary local files on the server, including the WordPress wp-config.php configuration file.

Exposure of wp-config.php reveals database credentials, authentication keys, and salts, enabling follow-on compromise of the entire WordPress installation.

Critical Impact
Remote, unauthenticated attackers can read sensitive configuration files, exposing database credentials and WordPress secret keys that enable full site takeover.

Affected Products

Ultimate Multisite WordPress plugin versions prior to 2.17.2
WordPress installations using the vulnerable plugin
Multisite WordPress deployments relying on this plugin for network management

Discovery Timeline

2026-10-14 - CVE-2026-107508 published to NVD
2026-10-14 - Last updated in NVD database

Technical Details for CVE-2026-107508

Vulnerability Analysis

The vulnerability is a Path Traversal and Local File Inclusion flaw classified under [CWE-22]. The Ultimate Multisite plugin accepts a file name parameter from user input and passes it to a file inclusion routine without sanitization or validation.

An attacker can supply traversal sequences such as ../../../../wp-config.php to escape the intended directory and read arbitrary files readable by the web server process. Because the endpoint requires no authentication, exploitation is trivial and can be performed with a single HTTP request.

Reading wp-config.php yields DB_USER, DB_PASSWORD, AUTH_KEY, SECURE_AUTH_KEY, and other secrets. These values allow attackers to forge session cookies, pivot to the database, or escalate to administrative access.

Root Cause

The plugin uses a user-controlled parameter to construct a file path passed to a PHP include or read function. No allowlist, canonicalization, or base-directory check is applied before the file operation.

Attack Vector

Exploitation occurs over the network against the public WordPress endpoint exposed by the plugin. The attacker sends a crafted request containing a path traversal payload in the vulnerable parameter. The server returns the contents of the targeted file or includes it in the response. See the WPScan Vulnerability Report for additional technical context.

Detection Methods for CVE-2026-107508

Indicators of Compromise

HTTP requests to Ultimate Multisite plugin endpoints containing ../ sequences or encoded variants such as %2e%2e%2f.
Access log entries referencing sensitive file names such as wp-config.php, /etc/passwd, or /proc/self/environ.
Unexpected outbound database connections or new administrative users following suspicious plugin requests.

Detection Strategies

Review web server access logs for requests to plugin URLs with traversal payloads or absolute paths.
Deploy Web Application Firewall (WAF) rules that block path traversal patterns targeting WordPress plugin parameters.
Correlate LFI probe attempts with subsequent authentication anomalies to identify successful exploitation.

Monitoring Recommendations

Enable verbose logging on the WordPress host and ingest logs into a centralized analytics platform.
Alert on reads of wp-config.php by the web server process outside normal application startup.
Monitor file integrity of WordPress core and plugin files to detect post-exploitation changes.

How to Mitigate CVE-2026-107508

Immediate Actions Required

Upgrade the Ultimate Multisite plugin to version 2.17.2 or later on all WordPress sites.
Rotate database credentials, AUTH_KEY, SECURE_AUTH_KEY, NONCE_KEY, and all salts defined in wp-config.php.
Audit WordPress user accounts and remove any unexpected administrative users created during the exposure window.
Review web server logs for traversal attempts dating back to the plugin's installation.

Patch Information

The vendor addressed the issue in Ultimate Multisite version 2.17.2 by adding validation of the user-supplied file parameter. Administrators should apply the update through the WordPress plugin manager or deploy it via their configuration management system. Refer to the WPScan Vulnerability Report for advisory details.

Workarounds

Deactivate the Ultimate Multisite plugin until the patched version can be deployed.
Apply WAF rules that block ../, ..%2f, and null-byte sequences on all plugin endpoints.
Restrict file system permissions so that the web server user cannot read wp-config.php directly where feasible.

bash

# Example WAF rule (ModSecurity) to block path traversal on plugin requests
SecRule REQUEST_URI "@contains /wp-content/plugins/ultimate-multisite/" \
  "chain,id:1070508,phase:2,deny,status:403,msg:'LFI attempt CVE-2026-107508'"
  SecRule ARGS "@rx (\.\./|\.\.%2f|%2e%2e/|wp-config\.php)"