CVE-2026-23842: ChatterBot Denial-of-Service Vulnerability

CVE-2026-23842 Overview

CVE-2026-23842 is a denial-of-service vulnerability affecting ChatterBot, a popular machine learning conversational dialog engine used for creating chat bots. The vulnerability stems from improper database session and connection pool management within the SQLAlchemy database layer. When multiple concurrent requests invoke the get_response() method, the underlying connection pool can become exhausted, leading to persistent service unavailability that requires a manual restart to recover.

Critical Impact

Applications using vulnerable ChatterBot versions can be rendered completely unavailable through concurrent API requests, requiring manual intervention to restore service.

Affected Products

• ChatterBot versions up to and including 1.2.10
• Applications utilizing ChatterBot's get_response() method with concurrent access patterns
• Python environments running vulnerable ChatterBot instances with SQLAlchemy backends

Discovery Timeline

• 2026-01-19 - CVE-2026-23842 published to NVD
• 2026-01-19 - Last updated in NVD database

Technical Details for CVE-2026-23842

Vulnerability Analysis

This denial-of-service vulnerability is classified under CWE-400 (Uncontrolled Resource Consumption). The flaw exists in how ChatterBot manages database sessions when handling the get_response() method. Under normal single-threaded operation, the connection pool management functions adequately. However, when the method is invoked concurrently—such as in web applications serving multiple users simultaneously—the improper session handling causes database connections to be consumed without proper release.

The vulnerability is particularly impactful for production deployments where ChatterBot serves as the backend for customer-facing chat interfaces. Each concurrent request can acquire a connection from the SQLAlchemy connection pool, and without proper cleanup, these connections remain held indefinitely. Once the pool is exhausted, all subsequent requests fail, and the service enters a degraded state from which it cannot automatically recover.

Root Cause

The root cause lies in improper database session lifecycle management within ChatterBot's storage adapter layer. When get_response() is called, database sessions are created to query training data and conversation history. In concurrent scenarios, these sessions are not properly closed or returned to the connection pool after use, leading to connection leakage. The SQLAlchemy connection pool has finite resources, and once all connections are consumed by leaked sessions, no new database operations can be performed.

Attack Vector

The attack vector is network-based and requires no authentication or user interaction. An attacker can exploit this vulnerability by simply sending multiple simultaneous requests to an application endpoint that invokes ChatterBot's get_response() method. This makes the vulnerability trivial to exploit—a basic script sending concurrent HTTP requests to a ChatterBot-powered chatbot interface can exhaust the connection pool within seconds, causing a complete denial of service.

The attack is particularly effective because:

• No special privileges or authentication are required
• The attack complexity is low—standard HTTP request flooding is sufficient
• The impact persists even after the attack stops, requiring manual restart
• Recovery time depends on administrative response time rather than automatic healing

Detection Methods for CVE-2026-23842

Indicators of Compromise

• Sudden increase in database connection errors or timeout messages in application logs
• SQLAlchemy pool exhaustion warnings such as QueuePool limit of size X overflow Y reached
• ChatterBot service becoming unresponsive while other application components remain functional
• Abnormal spike in concurrent requests to chatbot-related API endpoints

Detection Strategies

• Monitor SQLAlchemy connection pool metrics for pool exhaustion events
• Implement rate limiting on endpoints that invoke get_response() to detect abnormal request patterns
• Set up alerting for database connection timeout errors specific to ChatterBot storage operations
• Review application logs for patterns indicating connection leakage such as steadily increasing active connections

Monitoring Recommendations

• Configure database connection pool monitoring with alerts when utilization exceeds 80%
• Implement application performance monitoring (APM) to track get_response() method execution times and failure rates
• Set up log aggregation to correlate spikes in chatbot requests with database connection errors
• Establish baseline metrics for normal ChatterBot operation to identify anomalous behavior quickly

How to Mitigate CVE-2026-23842

Immediate Actions Required

• Upgrade ChatterBot to version 1.2.11 or later immediately
• Implement rate limiting on API endpoints that expose ChatterBot functionality
• Configure connection pool overflow limits and timeout values as temporary mitigation
• Prepare incident response procedures for manual service restart if exploitation occurs

Patch Information

The vulnerability has been fixed in ChatterBot version 1.2.11. The fix addresses the improper session management by ensuring database connections are properly released back to the pool after each get_response() invocation. Organizations should upgrade to this version as the primary remediation strategy.

For detailed patch information, refer to:

• GitHub Release 1.2.11
• GitHub Pull Request #2432
• GitHub Commit de89fe6
• GitHub Security Advisory GHSA-v4w8-49pv-mf72

Workarounds

• Implement request rate limiting at the web server or application level to reduce concurrent get_response() calls
• Configure SQLAlchemy connection pool with aggressive timeout settings to reclaim stale connections
• Deploy a request queue or throttling mechanism to serialize chatbot requests during high-traffic periods
• Consider deploying multiple isolated ChatterBot instances behind a load balancer to distribute connection pool load

# Configuration example - Rate limiting with nginx (temporary mitigation)
# Add to nginx location block serving ChatterBot endpoints
limit_req_zone $binary_remote_addr zone=chatbot_limit:10m rate=10r/s;

location /api/chat {
    limit_req zone=chatbot_limit burst=20 nodelay;
    proxy_pass http://chatterbot_backend;
}