CVE-2026-5803 Overview
CVE-2026-5803 is a server-side request forgery (SSRF) vulnerability affecting the bigsk1 openai-realtime-ui project up to commit 188ccde27fdf3d8fab8da81f3893468f53b2797c. The flaw resides in an unidentified function within the server.js file that implements the API Proxy Endpoint. Attackers can manipulate the Query argument to coerce the server into issuing arbitrary outbound HTTP requests. The vulnerability is remotely exploitable and a public exploit has been released. The project uses continuous delivery with rolling releases, so no fixed version is published. The patch is identified by commit hash 54f8f50f43af97c334a881af7b021e84b5b8310f.
Critical Impact
A remote authenticated attacker can abuse the API proxy to reach internal services, cloud metadata endpoints, or other restricted hosts reachable from the application server.
Affected Products
- bigsk1/openai-realtime-ui up to commit 188ccde27fdf3d8fab8da81f3893468f53b2797c
- Component: API Proxy Endpoint in server.js
- Fixed by commit 54f8f50f43af97c334a881af7b021e84b5b8310f
Discovery Timeline
- 2026-04-08 - CVE-2026-5803 published to NVD
- 2026-04-29 - Last updated in NVD database
Technical Details for CVE-2026-5803
Vulnerability Analysis
The openai-realtime-ui application exposes an API proxy endpoint implemented in server.js. The endpoint accepts a Query parameter and uses it to construct an outbound request without validating the destination. This pattern matches CWE-918: Server-Side Request Forgery. An attacker who can reach the proxy endpoint can supply arbitrary URLs and force the server to perform requests on the attacker's behalf. Because the request originates from the application host, it can reach resources that are otherwise unreachable from the public internet, including loopback services, internal management interfaces, and cloud instance metadata endpoints.
Root Cause
The API proxy does not enforce an allowlist of permitted destination hosts or schemes for the Query argument. User-controlled input flows directly into the server-side HTTP client without scheme validation, host resolution checks, or response filtering. As a result, requests targeting private address ranges and metadata services are not rejected. Refer to the patch commit for the maintainer's remediation approach.
Attack Vector
Exploitation requires network access to the API proxy endpoint and low-privilege credentials. The attacker submits a crafted Query value pointing at an internal URL such as a loopback address, a private network host, or a cloud metadata IP. The server fetches the URL and returns the response, leaking internal data. A public exploit reference is available in the BruceJqs public_exp issue tracker and the upstream issue.
No verified exploit code is reproduced here. Technical details are available in the linked references.
Detection Methods for CVE-2026-5803
Indicators of Compromise
- Outbound HTTP requests from the openai-realtime-ui host targeting private RFC1918 ranges, 127.0.0.0/8, or 169.254.169.254.
- Proxy endpoint access logs containing Query parameters with internal hostnames, IP literals, or non-HTTP schemes such as file:// or gopher://.
- Unexpected response sizes or content types returned from the proxy endpoint that indicate retrieval of internal service banners.
Detection Strategies
- Inspect server.js request logs for Query parameter values that resolve to internal or link-local addresses.
- Correlate egress firewall logs with the application host to identify proxied requests that bypass intended destinations.
- Apply CWE-918 detection signatures in web application firewalls to flag SSRF payload patterns.
Monitoring Recommendations
- Alert on any DNS lookups from the application host that resolve to private or loopback ranges.
- Monitor cloud instance metadata service (IMDS) access from application workloads and require IMDSv2 with session tokens.
- Track repeated failed proxy requests, which often indicate SSRF reconnaissance against internal port ranges.
How to Mitigate CVE-2026-5803
Immediate Actions Required
- Apply the upstream patch by updating to a build that includes commit 54f8f50f43af97c334a881af7b021e84b5b8310f.
- Restrict network egress from the application host to only the destinations required by the OpenAI proxy use case.
- Require IMDSv2 on cloud-hosted instances to prevent credential theft via SSRF.
Patch Information
The maintainer addressed the issue in commit 54f8f50f43af97c334a881af7b021e84b5b8310f, referenced in pull request #2. Because the project uses rolling releases without versioned tags, operators must pull the latest commit and redeploy. Additional context is available in VulDB entry #356242.
Workarounds
- Place the API proxy behind an egress allowlist that permits only the OpenAI API hostnames.
- Drop requests to private address ranges and 169.254.169.254 at the host firewall.
- Disable the proxy endpoint entirely if it is not required for production use.
# Example iptables egress allowlist restricting outbound HTTPS to OpenAI only
iptables -A OUTPUT -d 169.254.169.254 -j DROP
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 -p tcp --dport 443 -d api.openai.com -j ACCEPT
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
