CVE-2025-34060: Monero Forum PHP Object Injection RCE

CVE-2025-34060 Overview

A PHP object injection vulnerability exists in the Monero Project's Laravel-based forum software due to unsafe handling of untrusted input in the /get/image/ endpoint. The application passes a user-supplied link parameter directly to file_get_contents() without validation. MIME type checks using PHP's finfo can be bypassed via crafted stream filter chains that prepend spoofed headers, allowing access to internal Laravel configuration files. An attacker can extract the APP_KEY from config/app.php, forge encrypted cookies, and trigger unsafe unserialize() calls, leading to reliable remote code execution.

Critical Impact

This vulnerability allows unauthenticated attackers to achieve remote code execution by exploiting PHP object injection via crafted stream filter chains, enabling complete server compromise.

Affected Products

• Monero Project Laravel-based Forum Software

Discovery Timeline

• 2025-07-01 - CVE-2025-34060 published to NVD
• 2025-07-03 - Last updated in NVD database

Technical Details for CVE-2025-34060

Vulnerability Analysis

This vulnerability represents a chained attack that combines multiple weaknesses to achieve remote code execution. The core issue stems from improper input validation (CWE-20) in the /get/image/ endpoint, which accepts user-supplied URLs without adequate sanitization.

The attack chain works as follows: The application uses file_get_contents() to fetch remote images based on user input. While the application attempts to validate MIME types using PHP's finfo extension, this check can be bypassed using PHP stream filter chains. Attackers craft specially formatted stream wrappers that prepend fake MIME type headers to the response, tricking the validation logic.

Once the MIME check is bypassed, attackers can read arbitrary local files through the vulnerable endpoint. The primary target is Laravel's config/app.php file, which contains the APP_KEY - a cryptographic secret used for encrypting cookies and sessions. With this key in hand, attackers can forge valid encrypted cookies that contain serialized PHP objects.

When Laravel processes these forged cookies, it deserializes the attacker-controlled payload, triggering the PHP object injection. Using well-known Laravel gadget chains, the attacker achieves arbitrary code execution on the server.

Root Cause

The root cause is the lack of proper input validation on the link parameter passed to file_get_contents(). The function accepts various PHP stream wrappers beyond standard HTTP URLs, including php://filter chains that can manipulate file contents during retrieval. Combined with inadequate MIME type validation that relies solely on content inspection rather than strict URL allowlisting, this creates an exploitable file disclosure vulnerability. The secondary issue is Laravel's use of unserialize() on cookie data, which becomes dangerous once an attacker obtains the APP_KEY.

Attack Vector

The attack is network-based and requires no authentication or user interaction. An attacker submits a crafted request to the /get/image/ endpoint containing a malicious link parameter with PHP stream filter chains. These chains are designed to prepend valid image MIME type bytes to the beginning of sensitive configuration files, bypassing the finfo validation.

The attack sequence involves:

1. Crafting a PHP filter chain URL that reads config/app.php while prepending fake image headers
2. Extracting the APP_KEY from the response
3. Using the key to encrypt a serialized PHP gadget chain payload
4. Sending the malicious cookie to trigger deserialization and code execution

For detailed technical analysis and proof-of-concept details, see the Swap Blog Post and VulnCheck Security Advisory.

Detection Methods for CVE-2025-34060

Indicators of Compromise

• HTTP requests to /get/image/ endpoint containing php://filter or stream wrapper syntax in the link parameter
• Access attempts to config/app.php or other Laravel configuration files in server logs
• Unusual cookie values or session manipulation attempts following reconnaissance activity
• Evidence of file disclosure attempts in web application logs

Detection Strategies

• Monitor web server access logs for requests to /get/image/ with suspicious URL patterns including php://, file://, or data:// schemes
• Implement web application firewall (WAF) rules to block PHP stream wrapper patterns in user input
• Deploy runtime application self-protection (RASP) to detect and block file_get_contents() calls with unexpected protocols
• Monitor for signs of Laravel configuration file access or APP_KEY exposure

Monitoring Recommendations

• Enable verbose logging on the vulnerable endpoint to capture all link parameter values
• Set up alerts for requests containing stream wrapper patterns or path traversal sequences
• Monitor for unusual serialized PHP object patterns in incoming cookies
• Implement file integrity monitoring on Laravel configuration files

How to Mitigate CVE-2025-34060

Immediate Actions Required

• Restrict the /get/image/ endpoint to only accept HTTP and HTTPS URLs via strict allowlisting
• Implement URL validation that rejects any input containing PHP stream wrapper schemes
• Consider disabling the vulnerable endpoint entirely until a patch is available
• Rotate the Laravel APP_KEY if compromise is suspected and invalidate all existing sessions

Patch Information

Review the VulnCheck Security Advisory for the latest patch information and remediation guidance from the Monero Project.

Workarounds

• Deploy a web application firewall rule to block requests containing php://filter, file://, data://, or similar stream wrapper patterns
• Implement network segmentation to limit the impact of potential compromise
• Use PHP's allow_url_fopen and allow_url_include directives restrictively in php.ini
• Consider implementing a proxy layer that validates and sanitizes image URLs before passing them to the application

Example WAF rule to block PHP stream wrappers:

# Apache ModSecurity rule example
SecRule ARGS "@rx (?:php|file|data|glob|phar|zip|compress\.zlib|expect)://" \
    "id:100001,phase:2,deny,status:403,msg:'PHP stream wrapper blocked'"