CVE-2026-56399: Open WebUI SSRF Vulnerability in Retrieval Endpoint

Technical summary

CVE-2026-56399 is a server-side request forgery vulnerability in the /api/v1/retrieval/process/web endpoint of Open WebUI. The vulnerability exists because the endpoint insufficiently validates or filters URL parameters before making outbound requests, and fails to properly handle location redirect headers. An authenticated attacker can manipulate these parameters to bypass existing SSRF protections and reach internal services. The vulnerability is classified under CWE-918 (Server-Side Request Forgery), and the CVSS 3.1 vector reflects network-exploitable conditions with low attack complexity and low privilege requirements—specifically, the attacker must be authenticated to trigger the flaw.

Business impact

This vulnerability creates a pathway for insider threats or compromised accounts to reconnaissance and access internal infrastructure without triggering perimeter controls. If instance secrets or credentials are stored in environment variables or accessible via internal metadata services, attackers may escalate to command execution. For organizations running Open WebUI as a gateway to retrieval systems or knowledge bases, this could lead to unauthorized information disclosure or lateral movement into backend systems. The scope change in the CVSS vector indicates potential impact beyond the vulnerable component itself.

Affected systems

Open WebUI versions before 0.6.27 are affected. The /api/v1/retrieval/process/web endpoint is the specific attack surface. Any Open WebUI deployment accessible over a network where internal services (metadata endpoints, admin dashboards, databases, or other microservices) are reachable from the application's network namespace is at risk. Deployments with strict network segmentation between the application and internal resources have reduced exposure, but should not be considered safe without patching.

Exploitability

Exploitation requires valid authentication credentials—a user account, API key, or equivalent—meaning random internet scans cannot trigger this vulnerability. However, in environments with shared or default credentials, LDAP/SSO integration, or where API keys are widely distributed, the authentication barrier is lower than it appears. Once authenticated, the attack is straightforward: the attacker simply crafts a malicious URL parameter to the vulnerable endpoint and observes responses or timing to confirm access to internal services. No user interaction is required and the attack surface is direct.

Remediation

Upgrade Open WebUI to version 0.6.27 or later. This version contains fixes to properly validate and sanitize URL parameters, enforce destination allowlists, and reject suspicious redirect headers. After patching, restart the application and verify that the /api/v1/retrieval/process/web endpoint only accepts and processes URLs matching your organization's approved external retrieval sources. Review audit logs for any suspicious retrieval requests made before the patch was applied.

Patch guidance

Deploy Open WebUI 0.6.27 or later through your standard application update process. Verify the patch version post-deployment by checking the application version string in UI or via API endpoint. If your deployment uses container orchestration (Kubernetes, Docker Compose), update the image tag and redeploy. No database migrations or special configuration changes are required for this patch. Test the retrieval functionality with known-good external sources before considering the patch complete. Organizations running unsupported or end-of-life versions should prioritize upgrading to a supported release line to receive ongoing security updates.

Detection guidance

Monitor for POST or GET requests to /api/v1/retrieval/process/web with URL parameters pointing to RFC 1918 private IP addresses (10.0.0.0/8, 172.16.0.0/12, 192.168.0.0/16), localhost, or internal hostnames (e.g., 'admin', 'db', 'metadata'). Look for requests containing URL-encoded location headers or redirect chains. Check application logs for responses containing unusual content (YAML config, JSON environment dumps, error messages revealing internal service details) returned to authenticated users. Monitor outbound connections from the Open WebUI process to unexpected internal destinations, particularly on common internal service ports (5432, 3306, 8080, 9200). Correlate such requests with user accounts to identify potential compromises.

Why prioritize this

Although the CVSS score is Medium (5.0), this vulnerability bridges authentication to network traversal, making it a stepping stone for lateral movement and insider-threat scenarios. It is not currently in the CISA KEV catalog, reducing immediate pressure, but the attack complexity is low and the confidentiality impact is confirmed. Organizations should prioritize this based on whether they run Open WebUI with network access to sensitive backend systems, the sensitivity of those systems, and the trustworthiness of users with Open WebUI accounts. For multi-tenant or untrusted-user scenarios, elevate urgency.

Risk score, explained

CVSS 3.1 score of 5.0 (MEDIUM) reflects: network-accessible endpoint (AV:N), low attack complexity (AC:L), requirement for low privilege / authentication (PR:L), no user interaction (UI:N), scope change indicating impact beyond the component (S:C), and confirmed low confidentiality impact (C:L). The score does not account for likelihood of exploitation in insider-threat models or the bridge-building nature of SSRF in attack chains; security teams should layer organizational context atop the base score.

Frequently asked questions