CVE-2025-27817 identifies a critical server-side request forgery and arbitrary file read vulnerability in Apache Kafka Client that enables attackers to access unauthorized files and make unintended network requests through malicious SASL/OAUTHBEARER configuration parameters. This vulnerability affects Apache Kafka Client versions 3.1.0 through 3.9.0, achieving a CVSS score of 7.5 (High severity) with an EPSS score of 1.9 percentile, indicating significant risk for applications that accept untrusted Kafka client configurations. The vulnerability details reveal that attackers can exploit the "sasl.oauthbearer.token.endpoint.url" and "sasl.oauthbearer.jwks.endpoint.url" configuration parameters to read arbitrary file contents from the local filesystem or send requests to internal network resources, with file contents potentially exposed through error logging mechanisms. This creates substantial exploit risk for Apache Kafka deployments that allow untrusted configuration input, particularly affecting Apache Kafka Connect environments, SaaS products utilizing Kafka clients, and enterprise applications where configuration parameters can be influenced by external parties without proper validation and URL whitelisting controls. The technical root cause lies in Apache Kafka Client's SASL/OAUTHBEARER implementation where insufficient URL validation allows attackers to specify malicious URLs like "file:///etc/passwd" or internal service endpoints, classified as CWE-918 (Server-Side Request Forgery), creating a vector for known exploited vulnerabilities targeting distributed messaging systems through configuration parameter manipulation. The vulnerability specifically affects the client-side URL connection handling for token and JWKS retrieval, where the Kafka client attempts to fetch content from attacker-controlled URLs during SASL/OAUTHBEARER connection establishment, enabling both local file system access and internal network reconnaissance. The fix introduces a new system property "-Dorg.apache.kafka.sasl.oauthbearer.allowed.urls" to implement URL whitelisting, with version 3.9.1 maintaining backward compatibility by accepting all URLs by default, while version 4.0.0 and later require explicit URL configuration through an empty default whitelist. Mitigation strategies require upgrading to Apache Kafka Client version 3.9.1 or later and implementing proper URL whitelisting through the org.apache.kafka.sasl.oauthbearer.allowed.urls system property to restrict allowable endpoints for OAUTHBEARER authentication. Organizations should prioritize identifying all Kafka client deployments that accept external configuration input, audit SASL/OAUTHBEARER configurations for potential untrusted parameter sources, implement strict validation and whitelisting for all OAuth endpoint URLs, and maintain updated CVE database records to track similar SSRF vulnerabilities that could compromise distributed system security through configuration manipulation and unauthorized network access in messaging infrastructure and event streaming platforms.