CVE-2022-22979 - Spring Cloud Function Denial of Service Vulnerability in Prior Versions to 3.2.6 Due to Caching Issue in Function Catalog Component

In this blog post, we will delve into the details of a recently discovered security vulnerability in Spring Cloud Function (CVE-2022-22979). We will explore the issue itself, how it can be exploited, and how to mitigate the risk associated with it. This vulnerability affects versions of Spring Cloud Function prior to 3.2.6, enabling an attacker to potentially cause a denial-of-service (DoS) condition if they can directly interact with the framework provided lookup functionality.

I. Vulnerability Background

Spring Cloud Function is a popular framework that allows developers to write and deploy serverless functions using the Spring Framework. In the affected versions, a caching issue in the Function Catalog component may lead to a denial-of-service condition. The Function Catalog component is responsible for caching and providing access to declared functions within the framework.

Original Reference: Spring Cloud Function GitHub Repository

II. Exploit Details

To exploit this vulnerability, an attacker would need to directly interact with the framework provided lookup functionality. This interaction could be in the form of invoking the function directly or through any features that rely on function lookups. As a result, the Function Catalog cache may become filled with useless data, ultimately causing a denial-of-service condition.

III. Code Snippet Example

To help illustrate the issue, let's review a code snippet showing the caching behavior within the Function Catalog component:

public class FunctionCatalog {

    private final Map<String, FunctionInvocationWrapper> functionCache = new ConcurrentHashMap<>();

    public FunctionInvocationWrapper lookup(String functionName) {
        // If a function with the given name has already been cached, return its wrapper
        if (functionCache.containsKey(functionName)) {
            return functionCache.get(functionName);
        }

        FunctionInvocationWrapper functionWrapper = ... // Retrieve and wrap the function

        // Cache the wrapped function for future use
        functionCache.put(functionName, functionWrapper);

        return functionWrapper;
    }
}

In this example, we can see that the Function Catalog component caches function lookups, with the assumption that the functionName is uniquely identifying the function. However, if an attacker is manipulating the input strings (function names) to generate a large number of function lookups, the cache would grow indefinitely, inevitably causing a denial-of-service condition as system resources are consumed.

IV. Mitigation

To address this vulnerability, users should upgrade to Spring Cloud Function version 3.2.6 or a later release. This new version contains a fix that limits the caching of functions based on the configuration of the Function Catalog.

Original Reference: Spring Cloud Function Release Notes

If upgrading is not immediately possible, users may consider applying custom caching policies that limit the number of cached entries in the Function Catalog component, or implementing request throttling to limit the rate of function lookups.

V. Conclusion

In conclusion, CVE-2022-22979 demonstrates the potential security risks associated with caching mechanisms in software frameworks. By understanding the details of this vulnerability, developers and administrators can take the necessary steps to ensure their Spring Cloud Function deployments remain secure and less prone to denial-of-service attacks. Be sure to upgrade to the latest version and apply security best practices to protect your applications and infrastructure.

Timeline

Published on: 06/21/2022 15:15:00 UTC
Last modified on: 06/28/2022 19:12:00 UTC