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Jetty vulnerable to incorrect handling of invalid large TLS frame, exhausting CPU resources

High severity GitHub Reviewed Published Apr 1, 2021 in jetty/jetty.project • Updated Sep 26, 2023

Package

maven org.eclipse.jetty:jetty-server (Maven)

Affected versions

>= 7.2.2, < 9.4.39
>= 10.0.0, < 10.0.2
>= 11.0.0, < 11.0.2

Patched versions

9.4.39
10.0.2
11.0.2

Description

Impact

When using SSL/TLS with Jetty, either with HTTP/1.1, HTTP/2, or WebSocket, the server may receive an invalid large (greater than 17408) TLS frame that is incorrectly handled, causing CPU resources to eventually reach 100% usage.

Workarounds

The problem can be worked around by compiling the following class:

package org.eclipse.jetty.server.ssl.fix6072;

import java.nio.ByteBuffer;
import javax.net.ssl.SSLEngine;
import javax.net.ssl.SSLEngineResult;
import javax.net.ssl.SSLException;
import javax.net.ssl.SSLHandshakeException;

import org.eclipse.jetty.io.EndPoint;
import org.eclipse.jetty.io.ssl.SslConnection;
import org.eclipse.jetty.server.Connector;
import org.eclipse.jetty.server.SslConnectionFactory;
import org.eclipse.jetty.util.BufferUtil;
import org.eclipse.jetty.util.annotation.Name;
import org.eclipse.jetty.util.ssl.SslContextFactory;

public class SpaceCheckingSslConnectionFactory extends SslConnectionFactory
{
    public SpaceCheckingSslConnectionFactory(@Name("sslContextFactory") SslContextFactory factory, @Name("next") String nextProtocol)
    {
        super(factory, nextProtocol);
    }

    @Override
    protected SslConnection newSslConnection(Connector connector, EndPoint endPoint, SSLEngine engine)
    {
        return new SslConnection(connector.getByteBufferPool(), connector.getExecutor(), endPoint, engine, isDirectBuffersForEncryption(), isDirectBuffersForDecryption())
        {
            @Override
            protected SSLEngineResult unwrap(SSLEngine sslEngine, ByteBuffer input, ByteBuffer output) throws SSLException
            {
                SSLEngineResult results = super.unwrap(sslEngine, input, output);

                if ((results.getStatus() == SSLEngineResult.Status.BUFFER_UNDERFLOW ||
                    results.getStatus() == SSLEngineResult.Status.OK && results.bytesConsumed() == 0 && results.bytesProduced() == 0) &&
                    BufferUtil.space(input) == 0)
                {
                    BufferUtil.clear(input);
                    throw new SSLHandshakeException("Encrypted buffer max length exceeded");
                }
                return results;
            }
        };
    }
}

This class can be deployed by:

  • The resulting class file should be put into a jar file (eg sslfix6072.jar)
  • The jar file should be made available to the server. For a normal distribution this can be done by putting the file into ${jetty.base}/lib
  • Copy the file ${jetty.home}/modules/ssl.mod to ${jetty.base}/modules
  • Edit the ${jetty.base}/modules/ssl.mod file to have the following section:
[lib]
lib/sslfix6072.jar
  • Copy the file ${jetty.home}/etc/jetty-https.xml and${jetty.home}/etc/jetty-http2.xml to ${jetty.base}/etc
  • Edit files ${jetty.base}/etc/jetty-https.xml and ${jetty.base}/etc/jetty-http2.xml, changing any reference of org.eclipse.jetty.server.SslConnectionFactory to org.eclipse.jetty.server.ssl.fix6072.SpaceCheckingSslConnectionFactory. For example:
  <Call name="addIfAbsentConnectionFactory">
    <Arg>
      <New class="org.eclipse.jetty.server.ssl.fix6072.SpaceCheckingSslConnectionFactory">
        <Arg name="next">http/1.1</Arg>
        <Arg name="sslContextFactory"><Ref refid="sslContextFactory"/></Arg>
      </New>
    </Arg>
  </Call>
  • Restart Jetty

References

@waynebeaton waynebeaton published to jetty/jetty.project Apr 1, 2021
Published by the National Vulnerability Database Apr 1, 2021
Reviewed Apr 2, 2021
Published to the GitHub Advisory Database Apr 6, 2021
Last updated Sep 26, 2023

Severity

High
7.5
/ 10

CVSS base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

CVE ID

CVE-2021-28165

GHSA ID

GHSA-26vr-8j45-3r4w

Source code

Checking history
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