GitHub Security Advisory: GHSA-78fc-9688-w8xw
Package: org.openmrs.web:openmrs-web (MAVEN)
Severity: CRITICAL (CVSS 8.7)
CWE: CWE-22: Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Vulnerable versions: <= 2.7.8
Patched in: unpatched

Summary: OpenMRS Module Upload Vulnerable to Path Traversal (Zip Slip)

Details:
## Affected Versions

version ≤ 2.7.8 (latest version at time of disclosure)

https://github.com/openmrs/openmrs-core

## Impact

The endpoint `POST /openmrs/ws/rest/v1/module` is vulnerable to a path traversal (Zip Slip) attack. An authenticated attacker can upload a crafted `.omod` archive containing ZIP entries with directory traversal sequences. Upon automatic extraction by the server, the incomplete path validation in `WebModuleUtil.startModule()` fails to prevent entries such as `web/module/../../../../malicious.jsp` from being written outside the intended module directory. If the traversal target falls within the web application root (e.g., `/usr/local/tomcat/webapps/openmrs/`), the attacker achieves arbitrary file write and subsequent Remote Code Execution.

Notably, other extraction methods in the same codebase (`ModuleUtil.expandJar()`, `TestInstallUtil.addZippedTestModules()`) are properly protected with `normalize().startsWith()` checks — this vulnerability is an oversight where the same fix was not applied.

Furthermore, the `module.allow_web_admin` runtime property, which is intended to restrict administrators from managing modules via the web interface, only gates the Legacy UI controller entry point. The REST API endpoint `POST /openmrs/ws/rest/v1/module` does not check this property, allowing this restriction to be fully bypassed.

## Steps to Reproduce

1. Construct a malicious `.omod` file (which is a ZIP/JAR archive) containing a ZIP entry with a path traversal payload in its entry name, such as `web/module/../../../../<target_filename>`. Upload this file to `POST /openmrs/ws/rest/v1/module` with valid admin credentials via Basic Auth.

<img width="1986" height="1102" alt="image" src="https://github.com/user-attachments/assets/647f15de-7e8c-40b9-aba9-d4db5d2e0b52" />

<img width="2048" height="1078" alt="image" src="https://github.com/user-attachments/assets/301412a0-e3b0-4afb-91c2-e9739de3080d" />


2. The server parses and loads the module. During `WebModuleUtil.startModule()`, entries under `web/module/` are automatically extracted. The existing check `Paths.get(name).startsWith("..")` only blocks entries beginning with `..`, so an entry starting with `web/module/` passes the check. The `../` sequences in the remaining path cause the file to be written outside the intended `WEB-INF/view/module/` directory — for example, into the web application root at `/usr/local/tomcat/webapps/openmrs/`.

<img width="1439" height="141" alt="image" src="https://github.com/user-attachments/assets/4bda3b1e-a80e-42ed-af2b-a1da53e8db03" />

3. The traversed file is now accessible under the web application root. If the written file is a JSP script, accessing it via the browser triggers server-side execution, achieving RCE.

<img width="1482" height="300" alt="image" src="https://github.com/user-attachments/assets/61936002-78cd-4203-80f0-f0a8702b216c" />

## Root Cause Analysis

The vulnerability exists in `WebModuleUtil.startModule()` (`web/src