CVE-2023-34462: Netty handler Netty-handler SniHandler 16MB Allocation Vulnerability

MODERATE
Advisory Identifier: GHSA-6mjq-h674-j845
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CVSS 6.5
CWE-400 CWE-770
Published
Advisory Summary

CVE-2023-34462 is a MODERATE (CVSS 6.5) netty-handler snihandler 16mb allocation vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Netty handler libraries in the Maven ecosystem. The issue involves netty-handler snihandler 16mb allocation. Remediation is available by upgrading affected packages to version 4.1.94.Final.

CVE-2023-34462 at a Glance

CVE Identifier CVE-2023-34462
GHSA Identifier GHSA-6mjq-h674-j845
Severity MODERATE
CVSS v3.1 Base Score 6.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Netty handler
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 6.5

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required Low (PR:L)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality None (C:N)
Integrity None (I:N)
Availability High (A:H)

How to Fix CVE-2023-34462

To remediate this vulnerability, upgrade all affected Netty handler dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

io.netty:netty-handler fixed: 4.1.94.Final 
<dependency>
    <groupId>io.netty</groupId>
    <artifactId>netty-handler</artifactId>
    <version>4.1.94.Final</version>
</dependency>
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

mvn dependency:tree -Dincludes=io.netty

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2023-34462, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=io.netty

Analyze the terminal output to locate any version of Netty handler in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 4.1.94.Final), your application is affected.

Note: The mvn dependency:tree -Dincludes=io.netty command inspects the resolved dependency graph declared in your project's POM files; it does not perform automated security scanning or inspect runtime dynamic classpaths. Always verify runtime container classpaths and shaded JARs.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-400: Uncontrolled Resource Consumption, where the product does not properly control the allocation and maintenance of a limited resource. In Netty handler, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

### Summary The `SniHandler` can allocate up to 16MB of heap for each channel during the TLS handshake. When the handler or the channel does not have an idle timeout, it can be used to make a TCP server using the `SniHandler` to allocate 16MB of heap. ### Details The `SniHandler` class is a handler that waits for the TLS handshake to configure a `SslHandler` according to the indicated server name by the `ClientHello` record. For this matter it allocates a `ByteBuf` using the value defined in the `ClientHello` record. Normally the value of the packet should be smaller than the handshake packet but there are not checks done here and the way the code is written, it is possible to craft a packet that makes the `SslClientHelloHandler` 1/ allocate a 16MB `ByteBuf` 2/ not fail `decode` method `in` buffer 3/ get out of the loop without an exception The combination of this without the use of a timeout makes easy to connect to a TCP server and allocate 16MB of heap memory per connection. ### Impact If the user has no idle timeout handler configured it might be possible for a remote peer to send a client hello packet which lead the server to buffer up to 16MB of data per connection. This could lead to a OutOfMemoryError and so result in a DDOS.

CVE-2023-34462 Affected Netty handler Versions

1 component(s)
Fixed Versions:
4.1.94.Final
Product / Package Ecosystem Affected Versions Fixed Version
io.netty:netty-handler
maven/io.netty/netty-handler
Maven
< 4.1.94.Final
4.1.94.Final

References

GitHub Advisory / Wiki ADVISORY
https://github.com/netty/netty/security/advisories/GHSA-6mjq-h674-j845
NVD — CVE-2023-34462 NVD
https://nvd.nist.gov/vuln/detail/CVE-2023-34462
Security Fix Commit FIX COMMIT
https://github.com/netty/netty/commit/535da17e45201ae4278c0479e6162bb4127d4c32
Netty handler Source Repository REPOSITORY
https://github.com/netty/netty
Netty handler Security Information SECURITY
https://security.netapp.com/advisory/ntap-20230803-0001
Netty handler Security Information SECURITY
https://security.netapp.com/advisory/ntap-20240621-0007
Netty handler Security Information SECURITY
https://www.debian.org/security/2023/dsa-5558

Frequently Asked Questions

What is CVE-2023-34462?
CVE-2023-34462 is a security vulnerability in Netty handler involving netty-handler SniHandler 16MB allocation under CWE-400: Uncontrolled Resource Consumption.
Which Netty handler versions are affected?
Affected versions include releases prior to 4.1.94.Final across affected packages: io.netty:netty-handler.
What version fixes CVE-2023-34462?
Upgrading to 4.1.94.Final (or the latest patched release for your respective branch) resolves the vulnerability.
Is netty-handler affected?
Yes, io.netty:netty-handler is affected in releases prior to 4.1.94.Final. Upgrade your dependency to 4.1.94.Final or later.
What is the CVSS score of CVE-2023-34462?
CVE-2023-34462 has a CVSS v3.1 base score of 6.5 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2023-34462?
CVE-2023-34462 is classified under CWE-400: Uncontrolled Resource Consumption (The product does not properly control the allocation and maintenance of a limited resource.).
How can I check Maven dependencies for CVE-2023-34462?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=io.netty'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-6mjq-h674-j845",
  "modified" : "2024-06-24T21:24:21Z",
  "published" : "2023-06-20T16:33:22Z",
  "aliases" : [ "CVE-2023-34462" ],
  "summary" : "netty-handler SniHandler 16MB allocation",
  "details" : "### Summary\nThe `SniHandler` can allocate up to 16MB of heap for each channel during the TLS handshake. When the handler or the channel does not have an idle timeout, it can be used to make a TCP server using the `SniHandler` to allocate 16MB of heap.\n\n### Details\nThe `SniHandler` class is a handler that waits for the TLS handshake to configure a `SslHandler` according to the indicated server name by the `ClientHello` record. For this matter it allocates a `ByteBuf` using the value defined in the `ClientHello` record. \n\nNormally the value of the packet should be smaller than the handshake packet but there are not checks done here and the way the code is written, it is possible to craft a packet that makes the `SslClientHelloHandler`\n\n1/ allocate a 16MB `ByteBuf`\n2/ not fail `decode` method `in` buffer\n3/ get out of the loop without an exception\n\nThe combination of this without the use of a timeout makes  easy to connect to a TCP server and allocate 16MB of heap memory per connection.\n\n### Impact\nIf the user has no idle timeout handler configured it might be possible for a remote peer to send a client hello packet which lead the server to buffer up to 16MB of data per connection. This could lead to a OutOfMemoryError and so result in a DDOS.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "io.netty:netty-handler"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "4.1.94.Final"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/security/advisories/GHSA-6mjq-h674-j845"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2023-34462"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/netty/netty/commit/535da17e45201ae4278c0479e6162bb4127d4c32"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/netty/netty"
  }, {
    "type" : "WEB",
    "url" : "https://security.netapp.com/advisory/ntap-20230803-0001"
  }, {
    "type" : "WEB",
    "url" : "https://security.netapp.com/advisory/ntap-20240621-0007"
  }, {
    "type" : "WEB",
    "url" : "https://www.debian.org/security/2023/dsa-5558"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400", "CWE-770" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2023-06-20T16:33:22Z",
    "nvd_published_at" : "2023-06-22T23:15:09Z"
  }
}