Keycloak Cross-Site Scripting Vulnerability

A Cross-Site Scripting (XSS) vulnerability exists within Keycloak, a widely-used open-source identity and access management solution. This vulnerability allows a remote, authenticated attacker to inject malicious scripts into web pages viewed by other users. The attacker must possess valid credentials to initially access the vulnerable Keycloak instance. While the specific version affected is not provided in this advisory, it’s crucial for organizations using Keycloak to investigate and apply necessary patches or mitigations. The impact of successful exploitation ranges from defacement to sensitive data theft and account compromise. Defenders should prioritize patching Keycloak installations and implementing input validation to mitigate this risk.

Attack Chain

1. Attacker authenticates to the Keycloak instance with valid credentials.
2. Attacker identifies a vulnerable input field or parameter within the Keycloak application (e.g., user profile, group name, etc.).
3. Attacker crafts a malicious payload containing JavaScript code.
4. Attacker injects the malicious payload into the vulnerable input field.
5. The Keycloak application stores the malicious payload without proper sanitization.
6. A victim user (e.g., another authenticated user or an administrator) accesses the page containing the injected payload.
7. The victim’s browser executes the malicious JavaScript code.
8. The attacker can then steal cookies, redirect the user to a malicious site, or perform other actions on behalf of the victim.

Impact

Successful exploitation of this XSS vulnerability can lead to several negative consequences. An attacker could potentially steal session cookies, allowing them to impersonate other users, including administrators. This could grant them unauthorized access to sensitive data, configuration settings, and management functions. Furthermore, the attacker could deface the Keycloak interface, inject phishing scams, or redirect users to malicious websites. The number of victims depends on the number of users accessing the page with the injected XSS payload.

Recommendation

• Implement input validation and output encoding to prevent XSS attacks within Keycloak.
• Review Keycloak access logs for suspicious activity related to user profiles and injected scripts.
• Deploy the Sigma rule to detect possible XSS attempts in Keycloak logs.