CVE-2026-44203 in OpenAM
Summary
by MITRE • 09/15/2026
Open Access Management (OpenAM) is an access management solution. Prior to 16.1.1, the OAuth 2.0 and OpenID Connect authorization endpoint does not sufficiently encode user-supplied parameters before FormPostResponse.ftl and checkSession.ftl render them into HTML for the form_post response mode. An unauthenticated attacker can induce a user to open a crafted authorization request and execute script in the OpenAM origin. This issue is fixed in version 16.1.1.
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Analysis
by VulDB Data Team • 09/15/2026
The vulnerability identified in ForgeRock Access Management, formerly known as OpenAM, represents a critical flaw within its OAuth 2.0 and OpenID Connect implementation, specifically affecting versions prior to the release of patch level 16.1.1. This security defect centers on the improper handling of user-supplied parameters during the authorization endpoint processing phase. When an authentication or authorization request is processed by the server, specific input fields are passed through to template files named FormPostResponse.ftl and checkSession.ftl for rendering into HTML responses. The core technical failure lies in the insufficient encoding of these dynamic values before they are injected into the final HTML output structure used for form_post response modes. This lack of proper sanitization allows maliciously crafted input strings to bypass standard validation checks, effectively turning user-provided data into executable content within the context of the OpenAM application domain.
From a technical perspective, this flaw constitutes a classic instance of Cross-Site Scripting, specifically categorized under CWE-79 in the Common Weakness Enumeration taxonomy. The vulnerability arises because the server trusts input parameters without adequately escaping special characters that hold meaning in HTML and JavaScript contexts. When an unauthenticated attacker crafts a malicious authorization request containing embedded script tags or event handlers such as onerror or onload attributes, these payloads are stored within the response payload generated by the FreeMarker templates. Upon rendering, the browser interprets this content not merely as text but as executable code native to the OpenAM origin. This mechanism allows the attacker to inject arbitrary JavaScript that runs with the privileges of the trusted site, bypassing same-origin policy restrictions and enabling direct interaction with the application's Document Object Model.
The operational impact of this vulnerability is severe due to its potential for exploitation by unauthenticated actors. An attacker does not need valid credentials or prior access to initiate an attack vector; instead, they can lure a victim into clicking a specially crafted link that points to the OpenAM authorization endpoint with malicious parameters embedded in the query string. Once the user interacts with this request, their browser executes the injected script within the context of the OpenAM domain. This capability enables session hijacking, where the attacker can steal sensitive cookies such as JSESSIONID or OAuth access tokens, thereby gaining unauthorized control over the victim's authenticated sessions. Furthermore, it allows for credential harvesting through deceptive login forms that mimic legitimate interfaces but exfiltrate data to external servers controlled by the attacker. In enterprise environments relying on OpenAM for single sign-on and identity federation, this compromise can lead to broader lateral movement as attackers leverage stolen tokens to access downstream applications protected by the same identity provider.
Mitigation strategies must address both immediate remediation and long-term architectural resilience. The primary and most effective solution is to upgrade the ForgeRock Access Management instance to version 16.1.1 or later, where this encoding issue has been resolved in the underlying template rendering logic. For organizations unable to patch immediately due to operational constraints, temporary mitigations should focus on implementing a Web Application Firewall rule set that detects and blocks common XSS payloads within authorization request parameters before they reach the application server. Additionally, developers reviewing custom integrations with OpenAM must ensure strict input validation and output encoding are applied at every layer of data handling. It is also advisable to enforce Content Security Policy headers where possible to restrict script execution origins, although this serves as a secondary defense rather than a primary fix for this specific template injection flaw.
This vulnerability aligns with the MITRE ATT&CK framework technique T1059, which covers Command and Scripting Interpreter activities, specifically within the context of browser-based exploitation via client-side scripting. The attack vector corresponds to Initial Access techniques involving phishing or lure mechanisms where a user is induced to visit a malicious URL that triggers the vulnerability in their browser. Understanding this mapping helps security teams prioritize detection rules focused on anomalous patterns in authorization endpoint traffic and monitor for unusual script execution events within the OpenAM environment. By addressing this flaw, organizations not only close a direct path to account takeover but also strengthen their overall identity governance posture against sophisticated social engineering attacks that target authentication infrastructure components.