Apache Kafka Client - Arbitrary File Read (CVE-2025-27817)
Description
A possible arbitrary file read vulnerability has been identified in Apache Kafka Client. Apache Kafka Clients accept configuration data for setting the SASL/OAUTHBEARER connection with the brokers, including "sasl.oauthbearer.token.endpoint.url" and "sasl.oauthbearer.jwks.endpoint.url". Apache Kafka allows clients to read an arbitrary file and return the content in the error log, or sending requests to an unintended location. In applications where Apache Kafka Clients configurations can be specified by an untrusted party, attackers may use the "sasl.oauthbearer.token.endpoint.url" and "sasl.oauthbearer.jwks.endpoint.url" configuratin to read arbitrary contents of the disk and environment variables or make requests to an unintended location. In particular, this flaw may be used in Apache Kafka Connect to escalate from REST API access to filesystem/environment/URL access, which may be undesirable in certain environments, including SaaS products.
Since Apache Kafka 3.9.1/4.0.0, we have added a system property ("-Dorg.apache.kafka.sasl.oauthbearer.allowed.urls") to set the allowed urls in SASL JAAS configuration. In 3.9.1, it accepts all urls by default for backward compatibility. However in 4.0.0 and newer, the default value is empty list and users have to set the allowed urls explicitly.
psychologyCrowdSec Analysis
CVE-2025-27817 is a vulnerability in Apache Kafka Client that allows attackers to perform arbitrary file reads and server-side request forgery (SSRF) by manipulating SASL/OAUTHBEARER configuration URLs. If untrusted parties can specify client configurations, they may exploit this flaw to access sensitive files or environment variables and send requests to unintended locations, potentially escalating privileges in environments like Apache Kafka Connect. This vulnerability poses a significant risk in SaaS and multi-tenant deployments where configuration input is not tightly controlled.
CrowdSec has been tracking this vulnerability and its exploits since 8th of April 2026.
According to CrowdSec data, while opportunistic exploitation dominates, a portion of threat actors trying to exploit CVE-2025-27817 apply basic targeting methods such as port or service detection. This indicates emerging patterns of selective targeting. Telemetry from the CrowdSec network also shows that exploitation activity for CVE-2025-27817 remains steady week-over-week. Attack volumes are consistent with long-term trends, indicating sustained interest from threat actors. CVE-2025-27817 continues to be an active part of the threat landscape and will likely remain this way for the forseeable future.
Attackers exploit the /druid/indexer/v1/sampler endpoint by submitting crafted Kafka client configurations with sasl.oauthbearer.token.endpoint.url set to file:///etc/passwd, enabling arbitrary file read attempts on the server. This technique targets misconfigured Apache Kafka integrations to access sensitive files or trigger SSRF.
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| Event | Date |
|---|---|
| CVE Published | 2025-06-10 |
| Rule Released | 2026-04-08 |
| CrowdSec First Seen | 2026-04-08 |