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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

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v3 base metrics

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS v3 base metrics

Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

EPSS score

80.243%
(98th percentile)

CVE ID

CVE-2021-28165

GHSA ID

GHSA-26vr-8j45-3r4w

Source code

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