CVE-2025-10044 is a security vulnerability identified in the Red Hat build of Keycloak version 26.2. The issue arises from improper handling of the error_description query parameter in Keycloak's account console and other related pages. Specifically, arbitrary text supplied via this parameter is directly rendered on error pages without adequate validation or sanitization. Although the system applies HTML encoding which prevents classic cross-site scripting (XSS) attacks that execute malicious scripts, the vulnerability enables an attacker to craft URLs containing misleading or deceptive messages. These messages can include fake support phone numbers, URLs, or other social engineering content displayed within the trusted Keycloak user interface. This behavior creates a phishing vector, potentially tricking legitimate users into contacting malicious actors or divulging sensitive information. The vulnerability does not compromise confidentiality directly, nor does it allow code execution or denial of service, but it undermines user trust and can facilitate targeted phishing campaigns leveraging the trusted branding of Keycloak's UI. The CVSS v3.1 base score is 4.3 (medium severity), reflecting the network attack vector, low attack complexity, no privileges required, but requiring user interaction and resulting in integrity impact only. No known exploits are currently reported in the wild, and no patches or mitigations are explicitly linked in the provided data. This vulnerability highlights the importance of validating and sanitizing all user-controllable inputs, even when HTML encoding is applied, to prevent social engineering abuse within trusted interfaces.

For European organizations, particularly those using Red Hat's Keycloak 26.2 for identity and access management, this vulnerability can facilitate phishing attacks that exploit user trust in the authentication system. Since Keycloak is often deployed in enterprise environments to manage user authentication and authorization, misleading error messages could cause users to contact fraudulent support channels or disclose credentials or other sensitive information. This could lead to account compromise, unauthorized access to internal systems, or lateral movement within networks. While the vulnerability does not directly allow code execution or data leakage, the social engineering vector can be leveraged as an initial step in more complex attack chains. Organizations in sectors with high regulatory requirements for identity management, such as finance, healthcare, and government, may face increased risk due to the potential for credential theft or fraud. Additionally, phishing attacks exploiting this vulnerability could undermine user confidence in the organization's security posture and lead to reputational damage. The medium CVSS score indicates moderate risk, but the real-world impact depends heavily on user awareness and the sophistication of phishing attempts.

To mitigate this vulnerability, European organizations should implement the following specific measures: 1) Upgrade to a patched version of Red Hat Keycloak once available, as the vendor is likely to release a fix addressing proper input validation and sanitization of the error_description parameter. 2) In the interim, apply web application firewall (WAF) rules to detect and block suspicious query parameters containing misleading or phishing-related content targeting the error_description parameter. 3) Customize Keycloak error pages to remove or neutralize user-controllable content or replace dynamic error messages with static, generic messages that do not include user input. 4) Conduct user awareness training emphasizing caution when interacting with error messages and verifying support contact information through official channels. 5) Monitor logs and network traffic for anomalous URL patterns that exploit this parameter to launch phishing campaigns. 6) Employ Content Security Policy (CSP) headers to restrict the execution of unauthorized scripts and reduce the impact of potential XSS vectors. 7) Review and harden identity and access management policies to detect and respond to suspicious login or support request activities that may result from phishing attempts leveraging this vulnerability.