CVE-2026-2302: Mongoid Criteria RCE Vulnerability

CVE-2026-2302 Overview

CVE-2026-2302 is an arbitrary code execution vulnerability in MongoDB's Mongoid ODM (Object-Document Mapper) for Ruby. Under specific conditions, when processing a maliciously crafted value of type Hash, the Mongoid::Criteria.from_hash method may allow for executing arbitrary Ruby code. This vulnerability poses a significant risk to applications that pass untrusted user input to the from_hash method without proper validation.

Critical Impact

Successful exploitation of this vulnerability could allow remote attackers to execute arbitrary Ruby code on vulnerable systems, potentially leading to complete system compromise, data theft, or further lateral movement within the network.

Affected Products

• Mongoid ODM for Ruby (specific versions not disclosed)
• Ruby applications using vulnerable Mongoid::Criteria.from_hash implementations
• MongoDB-backed Ruby on Rails applications utilizing Mongoid

Discovery Timeline

• 2026-02-10 - CVE CVE-2026-2302 published to NVD
• 2026-02-10 - Last updated in NVD database

Technical Details for CVE-2026-2302

Vulnerability Analysis

This vulnerability falls under the category of Code Injection affecting the Mongoid ODM library. The Mongoid::Criteria.from_hash method is designed to construct query criteria from hash input, but under specific conditions, it fails to properly sanitize malicious input. When an attacker provides a specially crafted Hash value, the method may interpret certain hash keys or values as executable Ruby code rather than data parameters.

The vulnerability requires network access and low privileges, but also requires some user interaction for successful exploitation. The primary impact is to system integrity, as successful exploitation allows arbitrary code execution that can modify system state, inject malicious code, or tamper with application data.

Root Cause

The root cause of this vulnerability lies in improper input validation within the Mongoid::Criteria.from_hash method. The method fails to adequately sanitize or validate Hash input before processing, allowing specially crafted hash structures to be interpreted as executable code. This is a classic example of an Insecure Deserialization or Object Injection vulnerability pattern common in dynamic languages like Ruby, where hash or object instantiation can trigger unintended method calls or code evaluation.

Attack Vector

The attack vector is network-based, requiring the attacker to submit a maliciously crafted Hash value through an application interface that eventually passes the input to Mongoid::Criteria.from_hash. Attack scenarios may include:

1. Web forms or API endpoints that accept complex query parameters
2. JSON or YAML payloads that are deserialized into Ruby Hash objects
3. Any input path where user-controlled data reaches the vulnerable method

The vulnerability mechanism involves the unsafe processing of Hash input within Mongoid's criteria building functionality. When user-controlled Hash data containing specially crafted keys or values is passed to Mongoid::Criteria.from_hash, the method may evaluate certain constructs as Ruby code rather than treating them as literal data. For detailed technical information, refer to the MongoDB JIRA Ticket MONGOID-5919.

Detection Methods for CVE-2026-2302

Indicators of Compromise

• Unusual Ruby process activity or unexpected child processes spawned by the application
• Anomalous network connections originating from the Ruby application server
• Log entries showing malformed or suspicious Hash parameters in application requests
• Unexpected file system modifications in application directories

Detection Strategies

• Implement application-level logging for all calls to Mongoid::Criteria.from_hash with parameter inspection
• Deploy web application firewall (WAF) rules to detect suspicious Hash-like patterns in request payloads
• Monitor Ruby process behavior for unusual system calls or code execution patterns
• Review application logs for attempts to inject Ruby code constructs in query parameters

Monitoring Recommendations

• Enable detailed application logging for Mongoid query construction activities
• Implement runtime application self-protection (RASP) to detect code injection attempts
• Set up alerts for unusual database query patterns that may indicate exploitation attempts
• Monitor network traffic from application servers for unexpected outbound connections

How to Mitigate CVE-2026-2302

Immediate Actions Required

• Audit all code paths where user input reaches Mongoid::Criteria.from_hash and implement strict input validation
• Consider implementing allowlist-based filtering for Hash keys and values before passing to Mongoid
• Review and restrict the privileges of the Ruby application to minimize impact if exploitation occurs
• Temporarily disable or wrap vulnerable functionality if immediate patching is not possible

Patch Information

MongoDB has acknowledged this vulnerability through JIRA Ticket MONGOID-5919. Administrators should monitor the MongoDB security advisories and Mongoid gem releases for official patches. Update the Mongoid gem to the patched version as soon as it becomes available using bundle update mongoid.

Workarounds

• Implement a validation layer that sanitizes all Hash input before passing to Mongoid::Criteria.from_hash
• Use allowlisting to restrict acceptable Hash keys and value types in user input
• Consider wrapping the vulnerable method with a security proxy that validates input structure
• Deploy network-level controls to limit exposure of vulnerable application endpoints

# Configuration example - Input validation wrapper
# Add to your application's initializers or base controller

# Gemfile security update (when patch is available)
# bundle update mongoid

# Validate hash input before Mongoid processing
# Implement allowlist for permitted keys in your application layer
# Example: params.permit(:field1, :field2).to_h before passing to from_hash