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Description

The following analytic identifies the common URL requests used by a recent CVE - CVE-2022-22965, or Spring4Shell, to access a webshell on the remote webserver. The filename and cmd are arbitrary in this exploitation. Java will write a JSP to disk and a process will spawn from Java based on the cmd passed. This is indicative of typical web shell activity.

  • Type: TTP
  • Product: Splunk Enterprise, Splunk Enterprise Security, Splunk Cloud
  • Datamodel: Web
  • Last Updated: 2022-04-05
  • Author: Michael Haag, Splunk
  • ID: 2850c734-2d44-4431-8139-1a56f6f54c01

Annotations

ATT&CK
ID Technique Tactic
T1505.003 Web Shell Persistence
T1505 Server Software Component Persistence
T1190 Exploit Public-Facing Application Initial Access
Kill Chain Phase
  • Exploitation
NIST
  • DE.CM
CIS20
  • CIS 3
  • CIS 5
  • CIS 16
CVE
ID Summary CVSS
CVE-2022-22965 A Spring MVC or Spring WebFlux application running on JDK 9+ may be vulnerable to remote code execution (RCE) via data binding. The specific exploit requires the application to run on Tomcat as a WAR deployment. If the application is deployed as a Spring Boot executable jar, i.e. the default, it is not vulnerable to the exploit. However, the nature of the vulnerability is more general, and there may be other ways to exploit it. 7.5
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| tstats count from datamodel=Web where Web.http_method IN ("GET") Web.url IN ("*.jsp?cmd=*","*j&cmd=*") by Web.http_user_agent Web.http_method, Web.url,Web.url_length Web.src, Web.dest sourcetype 
| `drop_dm_object_name("Web")` 
| `security_content_ctime(firstTime)` 
| `security_content_ctime(lastTime)` 
| `web_jsp_request_via_url_filter`

Macros

The SPL above uses the following Macros:

Note that web_jsp_request_via_url_filter is a empty macro by default. It allows the user to filter out any results (false positives) without editing the SPL.

Required field

  • _time
  • Web.http_method
  • Web.url
  • Web.url_length
  • Web.src
  • Web.dest
  • Web.http_user_agent

How To Implement

To successfully implement this search you need to be ingesting information on Web traffic that include fields relavent for traffic into the Web datamodel.

Known False Positives

False positives may be present with legitimate applications. Attempt to filter by dest IP or use Asset groups to restrict to servers.

Associated Analytic story

RBA

Risk Score Impact Confidence Message
72.0 90 80 A suspicious URL has been requested against $dest$ by $src$, related to web shell activity.

Reference

Test Dataset

Replay any dataset to Splunk Enterprise by using our replay.py tool or the UI. Alternatively you can replay a dataset into a Splunk Attack Range

source | version: 1