CVE-2026-1518 is a Server-Side Request Forgery (SSRF) vulnerability identified in the Client Initiated Backchannel Authentication (CIBA) feature of the Red Hat Build of Keycloak. The flaw stems from insufficient validation of client-configured backchannel notification endpoints, which are URLs that Keycloak contacts to notify clients about authentication events. Because these endpoints are not properly validated, an attacker with high privileges (such as a registered client with configuration rights) can configure a malicious endpoint that causes Keycloak to send blind HTTP requests to internal or otherwise protected network resources. This could allow attackers to probe internal services, potentially leading to information disclosure or further exploitation. The vulnerability requires high privileges to exploit, does not require user interaction, and does not impact confidentiality or availability directly but can affect integrity by manipulating internal communications. The CVSS score of 2.7 reflects these factors, indicating low severity. No known exploits have been reported, and no official patches or workarounds have been detailed yet. The vulnerability highlights the importance of validating client-configured URLs and restricting server-side request capabilities to prevent SSRF attacks.

For European organizations, the impact of CVE-2026-1518 is generally low but context-dependent. Organizations using Red Hat Build of Keycloak with the CIBA feature enabled and allowing clients to configure backchannel notification endpoints are at risk. An attacker with sufficient privileges could leverage this vulnerability to perform SSRF attacks, potentially accessing internal network resources that are otherwise inaccessible externally. This could lead to reconnaissance of internal services, exposure of sensitive metadata, or pivoting to more critical systems. While the vulnerability does not directly compromise confidentiality or availability, it can undermine the integrity of internal communications and increase the attack surface. In highly regulated sectors such as finance, healthcare, or government within Europe, even low-severity SSRF vulnerabilities warrant prompt attention due to strict compliance requirements and the sensitivity of internal networks.

European organizations should implement the following specific mitigations: 1) Enforce strict validation and whitelisting of client-configured backchannel notification endpoints to ensure only trusted URLs are accepted. 2) Limit the network access of the Keycloak server, especially outbound HTTP requests, to prevent unauthorized internal resource access. 3) Monitor Keycloak logs and network traffic for unusual or unexpected outbound requests that could indicate exploitation attempts. 4) Apply the latest Red Hat security advisories and patches as they become available, even though no explicit patch links are currently provided. 5) Restrict client privileges to the minimum necessary, avoiding granting configuration rights to untrusted clients. 6) Consider disabling the CIBA feature if not required or deploying it in isolated environments. 7) Conduct regular security assessments and penetration testing focusing on SSRF vectors within authentication infrastructure.