CVE-2018-14655 in KeyCloak
Summary
by MITRE
A flaw was found in Keycloak 3.4.3.Final, 4.0.0.Beta2, 4.3.0.Final. When using 'response_mode=form_post' it is possible to inject arbitrary Javascript-Code via the 'state'-parameter in the authentication URL. This allows an XSS-Attack upon succesfully login.
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Analysis
by VulDB Data Team • 06/06/2023
The vulnerability identified as CVE-2018-14655 represents a critical cross-site scripting flaw within the Keycloak identity and access management platform. This security weakness affects multiple versions including 3.4.3.Final, 4.0.0.Beta2, and 4.3.0.Final, making it a widespread concern for organizations relying on this authentication framework. The flaw specifically manifests when the system employs the 'response_mode=form_post' parameter during authentication processes, creating an exploitable condition that enables malicious actors to inject arbitrary JavaScript code through the 'state' parameter in authentication URLs.
The technical implementation of this vulnerability stems from insufficient input validation and output encoding within Keycloak's authentication flow. When the 'state' parameter is improperly sanitized, it allows attackers to inject malicious JavaScript payloads that execute in the context of the victim's browser session. This occurs because the authentication URL construction process fails to properly escape or validate the state parameter contents before incorporating them into the form_post response mechanism. The 'state' parameter serves as a crucial security feature designed to prevent CSRF attacks by maintaining state information between the authentication request and response, but in this case it becomes a vector for XSS exploitation rather than a protective measure.
The operational impact of CVE-2018-14655 extends beyond simple code injection, as successful exploitation can lead to complete session hijacking and unauthorized access to protected resources. When a victim authenticates through a maliciously crafted URL containing the injected JavaScript, the payload executes in the legitimate user's browser context, potentially enabling attackers to steal session cookies, perform actions on behalf of authenticated users, or redirect users to malicious sites. This vulnerability directly violates the principle of least privilege and can compromise the integrity of the entire authentication ecosystem, particularly when users access sensitive applications through the compromised Keycloak instance. The attack vector is particularly insidious because it requires only a single click on a malicious link, making it highly effective for phishing campaigns targeting authenticated users.
Organizations should implement immediate mitigations including upgrading to patched versions of Keycloak where available, implementing proper input validation for the state parameter, and configuring web application firewalls to detect and block suspicious JavaScript patterns in authentication flows. The vulnerability aligns with CWE-79, which specifically addresses cross-site scripting flaws, and represents a clear violation of the ATT&CK framework's initial access techniques, particularly those involving malicious links and social engineering. Additionally, implementing Content Security Policy headers and ensuring proper parameter sanitization in all authentication flows will significantly reduce the attack surface for similar vulnerabilities. Security teams should also conduct comprehensive audits of their authentication flows to identify any other potential injection points that may present similar risks.