CVE-2022-39161 - How IBM WebSphere’s Plug-in Vulnerability Exposes Sensitive Data (Explained)

In September 2022, security researchers discovered a significant vulnerability CVE-2022-39161, affecting a broad range of IBM WebSphere Application Server versions (7.–9.), plus IBM WebSphere Liberty. The issue occurs when these servers interface with IBM’s Web Server Plug-ins — particularly in configurations using HTTPS and client-certificate authentication. If you administer IBM WebSphere infrastructures or work with sensitive enterprise data, understanding this flaw is critical.

In this post, I'll break down CVE-2022-39161, explain what went wrong (in plain English), show you relevant code/configuration snippets, and offer practical advice on detection and protection. This guide is based on IBM advisories, expert analysis, and my own research, making it an exclusive, easy-to-digest long read.

What is CVE-2022-39161?

IBM WebSphere Application Server (WAS) is a popular enterprise Java application server. Organizations often put a web server (like IBM HTTP Server, Apache, or Microsoft IIS) in front of WAS, using IBM’s Web Server Plug-ins to route traffic. These plug-ins help manage session affinity and various protocol concerns.

Unfortunately, in some configurations, the communication chain between the Web Server Plug-in and the back-end WAS is not fully secure even if HTTPS is used. This exposes a subtle but powerful *spoofing* and *man-in-the-middle* attack surface.

Official Description

> IBM WebSphere Application Server 7., 8., 8.5, 9., and IBM WebSphere Application Server Liberty, when configured to communicate with the Web Server Plug-ins, could allow an authenticated user to conduct spoofing attacks. A man-in-the-middle attacker could exploit the vulnerability using a certificate issued by a trusted authority to obtain sensitive information.

References

- NVD – CVE-2022-39161
- IBM Security Bulletin
- IBM X-Force ID: 235069

Visual Summary

[Browser/User] <-HTTPS-> [Web Server + Plug-in] <-HTTPS (broken)-> [WebSphere App Server]
                                             ^
                                           (Attacker controlling the connection)

Steps

1. Victim connects to your organization’s website using HTTPS, which lands on the front-end web server (IHS/Apache/IIS) running IBM’s Plug-in.

Web Server Plug-in talks to the back-end WebSphere server, typically using HTTPS.

3. *Insecure config*: If the plug-in trusts *any* valid CA-based certificate, an attacker can insert themselves between the plug-in and the application server, using a certificate from a legitimate (but not the right) CA.
4. *Result*: Attacker acts as a proxy or full MITM (Man-in-the-Middle), reading or altering unencrypted traffic.

Key Problem:
WebSphere’s plug-in does not enforce strict certificate validation or hostname verification by default — believing *any* CA-signed cert (instead of checking for the precise, known server cert).

Real-World Exploit Scenario

Suppose an attacker can poison DNS or otherwise get themselves in the network path (not trivial, but quite feasible in many enterprise environments). They issue a valid certificate (using something like LetsEncrypt or even a fake internal CA), present it to the plug-in, and traffic is silently intercepted.

plugin-cfg.xml sample (common vulnerable setup)

<Server>
  <Transport Hostname="appserver.internal" Port="9443" Protocol="https">
    <!-- no SSL attribute or no strict certificate definitions -->
  </Transport>
</Server>

In this setup, the plug-in will accept *any* certificate from a trusted CA and does not check the Hostname.

The plug-in calls Java SSL APIs roughly like this

SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(keyManagers, trustManagers, null);

SSLSocketFactory factory = sslContext.getSocketFactory();
SSLSocket socket = (SSLSocket) factory.createSocket(host, port);
// Does NOT verify hostname or certificate subject!

Fix: Use SSLParameters.setEndpointIdentificationAlgorithm("HTTPS"), which enforces hostname verification.

Is your plug-in version older than August 2022?

4. Have you ever set up custom certificate trust stores or hostname verification? If not, you are likely vulnerable.

Command-line check for plugin version (UNIX)

strings plugin-cfg.xml | grep version

Setup a local proxy with a valid, wrong-host certificate.

2. Point the plug-in to that proxy, restart the service, and see if it connects. If it does — you are vulnerable.

Exploitation in Practice (Proof-of-Concept)

*Disclaimer:* Only perform lawful, authorized testing!

PoC:

1. Generate a certificate for *evil-ca.com* signed by a trusted CA (e.g., LetsEncrypt), install on a MITM proxy.
2. Intercept plug-in traffic by modifying DNS or IP routing (e.g. /etc/hosts points appserver.internal → attacker IP).

Relay intercepted traffic to the real app server.

4. Read/request sensitive information from the WAS back-end.

Result: Login credentials, tokens, JSESSIONID cookies, and application payloads are exposed.

1. Update Your Plug-ins

IBM has patched this vulnerability in updated plug-in releases. Update immediately!

- IBM WebSphere Plug-in security update

### 2. Enforce Hostname/CN Verification

Configure plug-in components to require exact certificate match, not just “signed by any trusted CA”.

Example: Secure Plug-in Config with strict hostname check

<Server>
  <Transport Hostname="appserver.internal" Port="9443" Protocol="https" HostnameVerification="true"/>
</Server>

3. Use a Custom Trust Store

- Generate a private CA, sign your WAS server certificate, and install only *that* CA in the plug-in’s trust store.

5. Monitor Logs for Anomalous Connections

Alert on unexpected sources communicating with your WAS via HTTPS.

Conclusion

CVE-2022-39161 is a classic example of why *secure by default* matters. Even if you use HTTPS and trusted certificates, your applications remain at risk without rigorous endpoint verification — a subtle but catastrophic oversight in this case.

Always enforce strict hostname verification.

- Audit your SSL/TLS configurations, especially on internal links.
- Stay on top of IBM Security Bulletins for fixes.

Don’t wait for attackers to find you first. Patch and validate now!

*This guide is exclusive, summarized, and simplified for clarity by an independent security writer — not affiliated with IBM.*

Timeline

Published on: 05/03/2023 20:15:00 UTC
Last modified on: 05/12/2023 05:15:00 UTC