CVE-2026-5803: OpenAI Realtime UI SSRF Vulnerability

CVE-2026-5803 Overview

A Server-Side Request Forgery (SSRF) vulnerability has been discovered in bigsk1 openai-realtime-ui, affecting the server.js file within the API Proxy Endpoint component. The vulnerability allows attackers to manipulate Query arguments to forge server-side requests, potentially accessing internal resources or pivoting to other systems. The attack can be initiated remotely by authenticated users, and exploit details have been publicly released.

Critical Impact

This SSRF vulnerability enables attackers to abuse the server's trust relationships to access internal services, cloud metadata endpoints, or perform port scanning of internal networks, potentially leading to data exfiltration or lateral movement.

Affected Products

• bigsk1 openai-realtime-ui up to commit 188ccde27fdf3d8fab8da81f3893468f53b2797c
• API Proxy Endpoint component in server.js
• All versions prior to patch commit 54f8f50f43af97c334a881af7b021e84b5b8310f

Discovery Timeline

• April 8, 2026 - CVE-2026-5803 published to NVD
• April 8, 2026 - Last updated in NVD database

Technical Details for CVE-2026-5803

Vulnerability Analysis

This vulnerability is classified as CWE-918 (Server-Side Request Forgery). The SSRF flaw exists within the API Proxy Endpoint functionality implemented in server.js. The application fails to properly validate or sanitize user-controlled Query parameters before using them to construct server-side HTTP requests.

In SSRF attacks, the vulnerable server acts as a proxy for the attacker, allowing them to reach resources that would otherwise be inaccessible from the attacker's position. This is particularly dangerous in cloud environments where instance metadata services (such as AWS IMDSv1 at 169.254.169.254) may be accessible from the server.

The openai-realtime-ui project uses continuous delivery with rolling releases, meaning traditional version-based tracking is not applicable. Instead, specific Git commits identify vulnerable and patched states of the codebase.

Root Cause

The root cause of this vulnerability lies in insufficient input validation within the API Proxy Endpoint. The server.js component accepts Query arguments that influence the destination of server-side HTTP requests without implementing proper URL validation, allowlist checks, or scheme restrictions. This allows attackers to redirect requests to arbitrary internal or external destinations controlled by the attacker.

Attack Vector

The attack is network-based and requires low-privileged authentication to exploit. An attacker can craft malicious requests to the API Proxy Endpoint, manipulating Query parameters to target internal services, cloud metadata endpoints, or other sensitive resources. The exploit has been publicly disclosed, increasing the risk of active exploitation.

The vulnerability can be exploited to:

• Access internal services not exposed to the internet
• Query cloud provider metadata services for credentials
• Perform port scanning of internal networks
• Bypass firewall restrictions by using the server as a proxy

Technical details and proof-of-concept information can be found in the public vulnerability disclosure and the VulDB entry.

Detection Methods for CVE-2026-5803

Indicators of Compromise

• Unusual outbound requests from the server to internal IP ranges (10.x.x.x, 172.16.x.x, 192.168.x.x)
• Requests to cloud metadata endpoints (169.254.169.254, metadata.google.internal)
• Anomalous patterns in API Proxy Endpoint access logs showing requests to localhost or internal hostnames
• Network traffic from the application server to unexpected ports or services

Detection Strategies

• Monitor web application logs for Query parameters containing internal IP addresses, localhost references, or cloud metadata URLs
• Implement network-level monitoring to detect server-initiated connections to internal resources or metadata services
• Deploy web application firewall (WAF) rules to detect and block SSRF payload patterns in request parameters
• Use SentinelOne's behavioral AI to identify anomalous process network activity indicative of SSRF exploitation

Monitoring Recommendations

• Enable detailed logging for all API Proxy Endpoint requests, including full Query parameter values
• Configure alerts for DNS queries from the application server to internal hostnames or sensitive domains
• Implement egress traffic monitoring to detect unauthorized connections from the web server tier
• Review access logs for patterns consistent with SSRF probing, such as sequential internal IP scanning

How to Mitigate CVE-2026-5803

Immediate Actions Required

• Apply the security patch identified by commit 54f8f50f43af97c334a881af7b021e84b5b8310f immediately
• Implement URL allowlisting on the API Proxy Endpoint to restrict destinations to known-safe domains
• Block access to internal IP ranges and cloud metadata endpoints from the application layer
• Review logs for evidence of exploitation attempts prior to patching

Patch Information

The maintainers have released a patch addressing this vulnerability. The fix is available in commit 54f8f50f43af97c334a881af7b021e84b5b8310f. As this project uses continuous delivery with rolling releases, users should pull the latest version from the GitHub repository to ensure they have the patched code. Additional details about the vulnerability and fix can be found in GitHub Issue #1 and Pull Request #2.

Workarounds

• Implement network segmentation to prevent the application server from reaching sensitive internal resources
• Deploy a reverse proxy or WAF with SSRF protection rules in front of the application
• Use cloud provider IMDSv2 (or equivalent) to require session tokens for metadata access, mitigating SSRF-based credential theft
• Restrict outbound network access from the application server using firewall rules to an allowlist of necessary destinations

# Example iptables rules to restrict outbound connections from the application
# Block access to cloud metadata endpoints
iptables -A OUTPUT -d 169.254.169.254 -j DROP
iptables -A OUTPUT -d 169.254.169.253 -j DROP

# Block access to common internal IP ranges (adjust based on your network)
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