CVE-2023-20884: VMware Identity Manager Redirect Flaw

CVE-2023-20884 Overview

CVE-2023-20884 is an insecure redirect vulnerability affecting VMware Workspace ONE Access and VMware Identity Manager. The flaw stems from improper path handling within the authentication flow. An unauthenticated attacker can craft a malicious URL that redirects a victim to an attacker-controlled domain. Successful exploitation can lead to sensitive information disclosure, including credentials harvested via phishing pages hosted on the attacker domain. The vulnerability is tracked as an open redirect issue and is classified under [CWE-601]. VMware published advisory VMSA-2023-0011 to address the issue across affected products including VMware Cloud Foundation and VMware Identity Manager Connector.

Critical Impact

An unauthenticated attacker can redirect victims from a trusted VMware Workspace ONE Access or Identity Manager URL to an attacker-controlled domain, enabling credential theft and information disclosure through phishing.

Affected Products

• VMware Workspace ONE Access
• VMware Identity Manager (versions 3.3.6 and 3.3.7) and Identity Manager Connector
• VMware Cloud Foundation

Discovery Timeline

• 2023-05-30 - CVE-2023-20884 published to NVD
• 2025-01-10 - Last updated in NVD database

Technical Details for CVE-2023-20884

Vulnerability Analysis

The vulnerability is an open redirect flaw in the URL handling logic of VMware Workspace ONE Access and VMware Identity Manager. The application accepts user-supplied input as part of a redirect target without validating that the destination belongs to a trusted domain. Improper path handling allows the attacker to manipulate the redirect URL so that the browser ultimately lands on an external host.

Because the initial request originates from a legitimate VMware Workspace ONE Access or Identity Manager URL, the link appears trustworthy to users. Attackers leverage this trust to deliver phishing pages that mimic the legitimate VMware authentication portal. Victims entering credentials or session data on the cloned page expose sensitive information to the attacker. The flaw requires user interaction, typically clicking a crafted link, but no authentication on the target system.

The issue is tracked as [CWE-601] Open Redirect. The scope change reflected in the CVSS vector indicates that the impact extends beyond the vulnerable component to the user's browser session and any downstream resources accessed through the redirect.

Root Cause

The root cause is missing or insufficient validation of the redirect path parameter handled by the Workspace ONE Access and Identity Manager front-end. The application normalizes the path in a way that permits attacker-controlled hosts to be encoded into the redirect target. Without an allowlist of internal hosts or strict URL parsing, the server returns an HTTP redirect pointing to the external destination.

Attack Vector

The attack vector is network-based and requires user interaction. An attacker constructs a URL on the legitimate VMware host that includes an encoded redirect parameter pointing to a malicious domain. The attacker delivers the link via email, messaging, or a compromised web page. When the victim clicks the link, the Workspace ONE Access or Identity Manager server processes the request and issues a redirect to the attacker domain. The destination typically hosts a phishing page styled to match the VMware single sign-on portal, capturing credentials or tokens submitted by the victim.

No verified public proof-of-concept code is available for CVE-2023-20884. Refer to the VMware Security Advisory VMSA-2023-0011 for vendor technical details.

Detection Methods for CVE-2023-20884

Indicators of Compromise

• Outbound HTTP 302 responses from Workspace ONE Access or Identity Manager hosts containing Location headers pointing to non-corporate domains.
• Web access logs showing requests with redirect or return_url style parameters containing encoded external URLs, IP addresses, or unexpected protocol handlers.
• User reports of receiving links that begin with the legitimate Workspace ONE Access hostname but resolve to external login pages.
• Authentication anomalies such as logins from new geolocations shortly after users clicked Workspace ONE Access links delivered via email.

Detection Strategies

• Inspect web server and reverse proxy logs for redirect parameters whose decoded values reference hosts outside the organization's allowlist.
• Correlate email gateway URL telemetry with Workspace ONE Access access logs to identify campaigns abusing the trusted domain.
• Apply web application firewall (WAF) signatures that flag URL parameters containing http://, https://, or // sequences directed at external hosts.

Monitoring Recommendations

• Forward Workspace ONE Access, Identity Manager, and Identity Manager Connector logs to a centralized SIEM for redirect parameter analysis.
• Alert on user-agent and referrer mismatches that indicate a redirect chain originating from VMware infrastructure to unknown domains.
• Monitor identity provider sign-in logs for credential reuse from previously unseen IP addresses following suspected phishing events.

How to Mitigate CVE-2023-20884

Immediate Actions Required

• Apply the fixed versions listed in VMware Security Advisory VMSA-2023-0011 for Workspace ONE Access, Identity Manager, Identity Manager Connector, and VMware Cloud Foundation.
• Inventory all internet-exposed Workspace ONE Access and Identity Manager instances and prioritize patching of public-facing nodes first.
• Notify end users that they should validate the final URL of any Workspace ONE Access login page before entering credentials.

Patch Information

VMware addressed CVE-2023-20884 in the updates published with VMSA-2023-0011. Administrators should consult the advisory for the exact fixed build numbers for Workspace ONE Access (3.3.6, 3.3.7), Identity Manager Connector, and the corresponding VMware Cloud Foundation BOM versions. Apply patches following VMware's documented upgrade procedure and validate that redirect handling rejects external hosts after the upgrade.

Workarounds

• If patching cannot be performed immediately, restrict access to Workspace ONE Access and Identity Manager management interfaces to trusted networks via firewall or VPN.
• Deploy a reverse proxy or WAF rule that strips or validates redirect parameters before requests reach the Workspace ONE Access service.
• Educate users about the phishing risk and require multi-factor authentication so that captured passwords alone cannot complete a sign-in.