CVE-2023-49785: Nextchat SSRF Vulnerability

CVE-2023-49785 Overview

NextChat, also known as ChatGPT-Next-Web, is a popular cross-platform chat user interface designed for interacting with ChatGPT. A critical vulnerability has been identified in versions 2.11.2 and prior that exposes the application to server-side request forgery (SSRF) and cross-site scripting (XSS) attacks. This vulnerability enables attackers to gain read access to internal HTTP endpoints and perform write operations using HTTP POST, PUT, and other methods. Additionally, threat actors can leverage vulnerable NextChat instances as open proxies to mask their source IP addresses when forwarding malicious traffic to other internet targets.

Critical Impact

Unauthenticated attackers can exploit this vulnerability to access internal network resources, exfiltrate sensitive data, modify internal systems via HTTP methods, and use vulnerable instances as proxy servers to obscure the origin of malicious activities.

Affected Products

• NextChat (ChatGPT-Next-Web) versions 2.11.2 and prior
• All deployments exposing the application to the public internet
• Self-hosted NextChat instances without network isolation

Discovery Timeline

• March 12, 2024 - CVE CVE-2023-49785 published to NVD
• April 10, 2025 - Last updated in NVD database

Technical Details for CVE-2023-49785

Vulnerability Analysis

This vulnerability combines two dangerous attack vectors: Server-Side Request Forgery (SSRF) and Cross-Site Scripting (XSS). The SSRF component allows unauthenticated attackers to craft requests through the NextChat application that are then forwarded to internal or external destinations. This effectively transforms the NextChat deployment into an open proxy that can reach resources otherwise protected by network boundaries.

The vulnerability is particularly dangerous because it requires no authentication, can be exploited remotely over the network, and provides both read and write access to targeted endpoints. Attackers can probe internal infrastructure, access cloud metadata services, interact with internal APIs, and potentially pivot to other systems within the network. The XSS component further enables attackers to execute malicious scripts in the context of legitimate users' browsers, potentially leading to session hijacking or credential theft.

Root Cause

The root cause of this vulnerability lies in insufficient input validation and improper handling of user-controlled data within the NextChat application. The application fails to properly sanitize and validate URLs or destination endpoints before making server-side requests, allowing attackers to specify arbitrary targets. Additionally, user input is not adequately escaped before being rendered in responses, enabling the injection of malicious scripts that execute in victims' browsers.

Attack Vector

The attack is network-based and requires no authentication or user interaction. Attackers can exploit the SSRF vulnerability by sending specially crafted HTTP requests to the vulnerable NextChat instance, specifying internal network addresses or cloud metadata endpoints as the target. The application processes these requests and returns the responses to the attacker.

For the XSS component, attackers can inject malicious JavaScript payloads that execute when other users interact with the compromised content. The combination of these vulnerabilities significantly amplifies the attack surface, as SSRF can be used to access internal resources while XSS can target end users of the application.

Technical details and proof-of-concept information can be found in the Horizon3 Attack Blog and the Vicarius CVE-2023-49785 Analysis.

Detection Methods for CVE-2023-49785

Indicators of Compromise

• Unusual outbound HTTP requests from the NextChat server to internal IP ranges (e.g., 169.254.169.254, 10.x.x.x, 192.168.x.x)
• HTTP requests containing suspicious URL parameters targeting internal services or cloud metadata endpoints
• Unexpected traffic patterns showing the NextChat instance connecting to external destinations not associated with ChatGPT APIs
• JavaScript execution attempts or unusual script tags in request parameters or responses

Detection Strategies

• Monitor web application logs for requests containing internal IP addresses, localhost references, or cloud metadata service URLs
• Implement network-level monitoring to detect connections from NextChat servers to unexpected internal destinations
• Deploy web application firewalls (WAF) with rules to block common SSRF payloads and XSS injection patterns
• Analyze HTTP response sizes and content for anomalies that may indicate successful SSRF exploitation

Monitoring Recommendations

• Enable verbose logging on the NextChat application and review logs for suspicious request patterns
• Configure network intrusion detection systems (IDS) to alert on traffic from web servers to internal network segments
• Implement egress filtering and monitor for unauthorized outbound connections from application servers
• Set up alerts for any requests to cloud metadata services from application tier systems

How to Mitigate CVE-2023-49785

Immediate Actions Required

• Remove the NextChat application from public internet exposure immediately if possible
• Place NextChat deployments behind a VPN or corporate firewall to restrict access to authorized users only
• Deploy network segmentation to isolate NextChat instances from sensitive internal resources
• Implement a web application firewall (WAF) with SSRF and XSS protection rules

Patch Information

At the time of publication, no official patch was available for this vulnerability. A proposed fix has been submitted via GitHub Pull Request #4285. Users should monitor the GitHub repository and Issue #4283 for updates on the patch status and apply the fix as soon as it becomes available.

Workarounds

• Avoid exposing the NextChat application directly to the public internet
• If internet exposure is required, ensure the application runs on an isolated network segment with no access to internal resources
• Implement strict egress filtering to prevent the server from making requests to internal IP ranges or cloud metadata services
• Use reverse proxy configurations to add additional authentication layers before the NextChat application

# Example: Network isolation using iptables
# Block outbound connections to internal networks from NextChat server
iptables -A OUTPUT -d 10.0.0.0/8 -j DROP
iptables -A OUTPUT -d 172.16.0.0/12 -j DROP
iptables -A OUTPUT -d 192.168.0.0/16 -j DROP
iptables -A OUTPUT -d 169.254.169.254/32 -j DROP