CVE-2021-3629: Undertow core Remote Code Execution Vulnerability

HIGH
Advisory Identifier: GHSA-rf6q-vx79-mjxr
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CVSS 7.5
CWE-400
Published
Advisory Summary

CVE-2021-3629 is a HIGH (CVSS 7.5) remote code execution vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Undertow core libraries in the Maven ecosystem. The issue involves undertow uncontrolled resource consumption. Remediation is available by upgrading affected packages to version 2.0.40.Final, 2.2.11.Final.

CVE-2021-3629 at a Glance

CVE Identifier CVE-2021-3629
GHSA Identifier GHSA-rf6q-vx79-mjxr
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Undertow core
Package Ecosystem Maven
Published Date
Last Updated

Security Impact

CVSS: 7.5

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

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
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-2021-3629

To remediate this vulnerability, upgrade all affected Undertow core 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.undertow:undertow-core fixed: 2.0.40.Final 
<dependency>
    <groupId>io.undertow</groupId>
    <artifactId>undertow-core</artifactId>
    <version>2.0.40.Final</version>
</dependency>
io.undertow:undertow-core fixed: 2.2.11.Final 
<dependency>
    <groupId>io.undertow</groupId>
    <artifactId>undertow-core</artifactId>
    <version>2.2.11.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.undertow

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2021-3629, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=io.undertow

Analyze the terminal output to locate any version of Undertow core in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.0.40.Final), your application is affected.

Note: The mvn dependency:tree -Dincludes=io.undertow 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 Undertow core, 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

A flaw was found in Undertow. A potential security issue in flow control handling by the browser over HTTP/2 may potentially cause overhead or a denial of service in the server. The highest threat from this vulnerability is availability. This flaw affects Undertow versions prior to 2.0.40.Final and prior to 2.2.11.Final.

CVE-2021-3629 Affected Undertow core Versions

2 component(s)
Fixed Versions:
2.0.40.Final2.2.11.Final
Product / Package Ecosystem Affected Versions Fixed Version
io.undertow:undertow-core
maven/io.undertow/undertow-core
Maven
< 2.0.40.Final
2.0.40.Final
io.undertow:undertow-core
maven/io.undertow/undertow-core
Maven
≥ 2.1.0
< 2.2.11.Final
2.2.11.Final

References

NVD — CVE-2021-3629 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-3629
bugzilla.redhat.com/show_bug.cgi WEB
https://bugzilla.redhat.com/show_bug.cgi?id=1977362
Undertow core Source Repository REPOSITORY
https://github.com/undertow-io/undertow
Undertow core Security Information SECURITY
https://security.netapp.com/advisory/ntap-20220729-0008

Frequently Asked Questions

What is CVE-2021-3629?
CVE-2021-3629 is a security vulnerability in Undertow core involving Undertow Uncontrolled Resource Consumption under CWE-400: Uncontrolled Resource Consumption.
Which Undertow core versions are affected?
Affected versions include releases prior to 2.0.40.Final, 2.2.11.Final across affected packages: io.undertow:undertow-core.
What version fixes CVE-2021-3629?
Upgrading to 2.0.40.Final, 2.2.11.Final (or the latest patched release for your respective branch) resolves the vulnerability.
Is undertow-core affected?
Yes, io.undertow:undertow-core is affected in releases prior to 2.0.40.Final, 2.2.11.Final. Upgrade your dependency to 2.0.40.Final, 2.2.11.Final or later.
What is the CVSS score of CVE-2021-3629?
CVE-2021-3629 has a CVSS v3.1 base score of 7.5 (HIGH) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.
What CWE is associated with CVE-2021-3629?
CVE-2021-3629 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-2021-3629?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=io.undertow'. 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-rf6q-vx79-mjxr",
  "modified" : "2025-06-12T16:03:19Z",
  "published" : "2022-05-25T00:00:22Z",
  "aliases" : [ "CVE-2021-3629" ],
  "summary" : "Undertow Uncontrolled Resource Consumption",
  "details" : "A flaw was found in Undertow. A potential security issue in flow control handling by the browser over HTTP/2 may potentially cause overhead or a denial of service in the server. The highest threat from this vulnerability is availability. This flaw affects Undertow versions prior to 2.0.40.Final and prior to 2.2.11.Final.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "io.undertow:undertow-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "0"
      }, {
        "fixed" : "2.0.40.Final"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.0.39.Final"
    }
  }, {
    "package" : {
      "ecosystem" : "Maven",
      "name" : "io.undertow:undertow-core"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "2.1.0"
      }, {
        "fixed" : "2.2.11.Final"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 2.2.10.Final"
    }
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-3629"
  }, {
    "type" : "WEB",
    "url" : "https://bugzilla.redhat.com/show_bug.cgi?id=1977362"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/undertow-io/undertow"
  }, {
    "type" : "WEB",
    "url" : "https://security.netapp.com/advisory/ntap-20220729-0008"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-05-25T22:41:25Z",
    "nvd_published_at" : "2022-05-24T19:15:00Z"
  }
}