Denial of Service Vulnerability in libspring-java: ETag Header Parsing Flaw

Background

libspring-java is a library used in Java applications to facilitate the development of web applications. It provides essential features for building robust and scalable applications. However, certain versions of this library are vulnerable to a Denial of Service (DoS) attack due to improper handling of ETags in 'If-Match' and 'If-None-Match' request headers.

Vulnerability Detail

The vulnerability arises from the way applications parse ETags from the 'If-Match' or 'If-None-Match' request headers. Attackers can exploit this flaw by sending specially crafted requests that cause the application to consume excessive resources, leading to a Denial of Service. This can result in application downtime, affecting availability and user experience. The vulnerability is present in all versions of libspring-java, making it critical for users to address it promptly.

Workaround

For users of older, unsupported versions, a temporary workaround is to enforce a size limit on the 'If-Match' and 'If-None-Match' headers. This can be implemented through a Filter in your application. Here is a sample code snippet in Java:

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;

public class ETagSizeLimitFilter implements Filter { private static final int MAX_HEADER_SIZE = 1024; // Set your size limit here

@Override
public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) throws IOException, ServletException {

        if (request instanceof HttpServletRequest) {

        HttpServletRequest httpRequest = (HttpServletRequest) request;
        String ifMatch = 

httpRequest.getHeader("If-Match");

        String ifNoneMatch = 

httpRequest.getHeader("If-None-Match");

if ((ifMatch != null && ifMatch.length() > MAX_HEADER_SIZE) || (ifNoneMatch != null && ifNoneMatch.length() > MAX_HEADER_SIZE)) {
                throw new ServletException("ETag header size exceeds limit");
            }
        }
        chain.doFilter(request, response);
    }

@Override
public void init(FilterConfig filterConfig) throws ServletException {}

@Override
public void destroy() {}

}

Conclusion

The CVE-2024-38809 vulnerability in libspring-java poses a significant risk of Denial of Service attacks due to improper handling of ETags. Users are strongly encouraged to upgrade to the latest version or implement the suggested workaround to mitigate the risk. Monitoring tools like Vulert can assist in identifying vulnerabilities in your applications.

See every vulnerability recorded for libspring-java →

FAQ