CVE-2020-11996: Apache Tomcat Remote Code Execution Vulnerability

HIGH
Advisory Identifier: GHSA-53hp-jpwq-2jgq
Share
CVSS 7.5
CWE-400
Published
Advisory Summary

CVE-2020-11996 is a HIGH (CVSS 7.5) remote code execution vulnerability (CWE-400: Uncontrolled Resource Consumption) affecting Apache Tomcat libraries in the Maven ecosystem. The issue involves uncontrolled resource consumption in apache tomcat. Remediation is available by upgrading affected packages to version 10.0.0-M5, 9.0.35, 8.5.55.

CVE-2020-11996 at a Glance

CVE Identifier CVE-2020-11996
GHSA Identifier GHSA-53hp-jpwq-2jgq
Severity HIGH
CVSS v3.1 Base Score 7.5
CWE Classification CWE-400: Uncontrolled Resource Consumption
Affected Product Apache Tomcat
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-2020-11996

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

org.apache.tomcat:tomcat fixed: 10.0.0-M5 
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat</artifactId>
    <version>10.0.0-M5</version>
</dependency>
org.apache.tomcat:tomcat fixed: 9.0.35 
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat</artifactId>
    <version>9.0.35</version>
</dependency>
org.apache.tomcat:tomcat fixed: 8.5.55 
<dependency>
    <groupId>org.apache.tomcat</groupId>
    <artifactId>tomcat</artifactId>
    <version>8.5.55</version>
</dependency>
org.apache.tomcat.embed:tomcat-embed-core fixed: 10.0.0-M5 
<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-core</artifactId>
    <version>10.0.0-M5</version>
</dependency>
org.apache.tomcat.embed:tomcat-embed-core fixed: 9.0.35 
<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-core</artifactId>
    <version>9.0.35</version>
</dependency>
org.apache.tomcat.embed:tomcat-embed-core fixed: 8.5.55 
<dependency>
    <groupId>org.apache.tomcat.embed</groupId>
    <artifactId>tomcat-embed-core</artifactId>
    <version>8.5.55</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=org.apache.tomcat

How to Check if You Are Affected

To determine whether your Java application is affected by CVE-2020-11996, inspect your build dependencies using the Maven Dependency Plugin:

mvn dependency:tree -Dincludes=org.apache.tomcat

Analyze the terminal output to locate any version of Apache Tomcat in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 10.0.0-M5), your application is affected.

Note: The mvn dependency:tree -Dincludes=org.apache.tomcat 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 Apache Tomcat, 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 specially crafted sequence of HTTP/2 requests sent to Apache Tomcat 10.0.0-M1 to 10.0.0-M5, 9.0.0.M1 to 9.0.35 and 8.5.0 to 8.5.55 could trigger high CPU usage for several seconds. If a sufficient number of such requests were made on concurrent HTTP/2 connections, the server could become unresponsive.

CVE-2020-11996 Affected Apache Tomcat Versions

6 component(s)
Fixed Versions:
10.0.0-M59.0.358.5.55
Product / Package Ecosystem Affected Versions Fixed Version
org.apache.tomcat:tomcat
maven/org.apache.tomcat/tomcat
Maven
≥ 10.0.0-M1
< 10.0.0-M5
10.0.0-M5
org.apache.tomcat:tomcat
maven/org.apache.tomcat/tomcat
Maven
≥ 9.0.0.M1
< 9.0.35
9.0.35
org.apache.tomcat:tomcat
maven/org.apache.tomcat/tomcat
Maven
≥ 8.5.0
< 8.5.55
8.5.55
org.apache.tomcat.embed:tomcat-embed-core
maven/org.apache.tomcat.embed/tomcat-embed-core
Maven
≥ 10.0.0-M1
< 10.0.0-M5
10.0.0-M5
org.apache.tomcat.embed:tomcat-embed-core
maven/org.apache.tomcat.embed/tomcat-embed-core
Maven
≥ 9.0.0.M1
< 9.0.35
9.0.35
org.apache.tomcat.embed:tomcat-embed-core
maven/org.apache.tomcat.embed/tomcat-embed-core
Maven
≥ 8.5.0
< 8.5.55
8.5.55

References

NVD — CVE-2020-11996 NVD
https://nvd.nist.gov/vuln/detail/CVE-2020-11996
Security Fix Commit FIX COMMIT
https://github.com/apache/tomcat/commit/9434a44d3449d620b1be70206819f8275b4a7509
Security Fix Commit FIX COMMIT
https://github.com/apache/tomcat/commit/9a0231683a77e2957cea0fdee88b193b30b0c976
Security Fix Commit FIX COMMIT
https://github.com/apache/tomcat/commit/c8acd2ab7371e39aeca7c306f3b5380f00afe552
lists.apache.org/thread.html/rb820f1... WEB
https://lists.apache.org/thread.html/rb820f1a2a02bf07414be12c653c2ab5321fd87b9bf6c5e635c53ff4b@%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org/thread.html/rc80b96... WEB
https://lists.apache.org/thread.html/rc80b96b4b96618b2b7461cb90664a428cfd6605eea9f74e51b792542@%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org/thread.html/rea65d6... WEB
https://lists.apache.org/thread.html/rea65d6ef2e45dd1c45faae83922042732866c7b88fa109b76c83db52@%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org/thread.html/ref0339... WEB
https://lists.apache.org/thread.html/ref0339792ac6dac1dba83c071a727ad72380899bde60f6aaad4031b9@%3Cnotifications.ofbiz.apache.org%3E
lists.debian.org/debian-lts-announce... WEB
https://lists.debian.org/debian-lts-announce/2020/07/msg00010.html
Apache Tomcat Security Information SECURITY
https://security.netapp.com/advisory/ntap-20200709-0002
Apache Tomcat Security Information SECURITY
https://tomcat.apache.org/security-10.html
Apache Tomcat Security Information SECURITY
https://tomcat.apache.org/security-8.html
Apache Tomcat Security Information SECURITY
https://tomcat.apache.org/security-9.html
usn.ubuntu.com/4596-1 WEB
https://usn.ubuntu.com/4596-1
Apache Tomcat Security Information SECURITY
https://www.debian.org/security/2020/dsa-4727
Apache Tomcat Security Information SECURITY
https://www.oracle.com/security-alerts/cpujan2021.html
Apache Tomcat Security Information SECURITY
https://www.oracle.com/security-alerts/cpuoct2020.html
lists.apache.org/thread.html/rb4ee49... WEB
https://lists.apache.org/thread.html/rb4ee49ecc4c59620ffd5e66e84a17e526c2c3cfa95d0cd682d90d338@%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org/thread.html/ra7092f... WEB
https://lists.apache.org/thread.html/ra7092f7492569b39b04ec0decf52628ba86c51f15efb38f5853e2760@%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org/thread.html/r9ad911... WEB
https://lists.apache.org/thread.html/r9ad911fe49450ed9405827af0e7a74104041081ff91864b1f2546bbd@%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org/thread.html/r93ca62... WEB
https://lists.apache.org/thread.html/r93ca628ef3a4530dfe5ac49fddc795f0920a4b2a408b57a30926a42b@%3Ccommits.ofbiz.apache.org%3E
lists.apache.org/thread.html/r8f7484... WEB
https://lists.apache.org/thread.html/r8f7484589454638af527182ae55ef5b628ba00c05c5b11887c922fb1@%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org/thread.html/r8f3d41... WEB
https://lists.apache.org/thread.html/r8f3d416c193bc9384a8a7dd368623d441f5fcaff1057115008100561@%3Ccommits.ofbiz.apache.org%3E
Apache Tomcat Source Repository REPOSITORY
https://github.com/apache/tomcat
lists.apache.org/thread.html/r74f5a8... WEB
https://lists.apache.org/thread.html/r74f5a8204efe574cbfcd95b2a16236fe95beb45c4d9fee3dc789dca9@%3Ccommits.ofbiz.apache.org%3E
lists.apache.org/thread.html/r6c2980... WEB
https://lists.apache.org/thread.html/r6c29801370a36c1a5159679269777ad0c73276d3015b8bbefea66e5c@%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org/thread.html/r5a4f80... WEB
https://lists.apache.org/thread.html/r5a4f80a6acc6607d61dae424b643b594c6188dd4e1eff04705c10db2@%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org/thread.html/r5541ef... WEB
https://lists.apache.org/thread.html/r5541ef6b6b68b49f76fc4c45695940116da2bcbe0312ef204a00a2e0%40%3Cannounce.tomcat.apache.org%3E
lists.apache.org/thread.html/r3ea96d... WEB
https://lists.apache.org/thread.html/r3ea96d8f36dd404acce83df8aeb22a9e807d6c13ca9c5dec72f872cd@%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org/thread.html/r252901... WEB
https://lists.apache.org/thread.html/r2529016c311ce9485e6f173446d469600fdfbb94dccadfcd9dfdac79@%3Cusers.tomcat.apache.org%3E
Apache Tomcat Security Information SECURITY
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00064.html
Apache Tomcat Security Information SECURITY
http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00072.html

Frequently Asked Questions

What is CVE-2020-11996?
CVE-2020-11996 is a security vulnerability in Apache Tomcat involving Uncontrolled Resource Consumption in Apache Tomcat under CWE-400: Uncontrolled Resource Consumption.
Which Apache Tomcat versions are affected?
Affected versions include releases prior to 10.0.0-M5, 9.0.35, 8.5.55 across affected packages: org.apache.tomcat:tomcat, org.apache.tomcat.embed:tomcat-embed-core.
What version fixes CVE-2020-11996?
Upgrading to 10.0.0-M5, 9.0.35, 8.5.55 (or the latest patched release for your respective branch) resolves the vulnerability.
Is tomcat affected?
Yes, org.apache.tomcat:tomcat is affected in releases prior to 10.0.0-M5, 9.0.35, 8.5.55. Upgrade your dependency to 10.0.0-M5, 9.0.35, 8.5.55 or later.
Is tomcat-embed-core affected?
Yes, org.apache.tomcat.embed:tomcat-embed-core is affected in releases prior to 10.0.0-M5, 9.0.35, 8.5.55. Upgrade your dependency to 10.0.0-M5, 9.0.35, 8.5.55 or later.
What is the CVSS score of CVE-2020-11996?
CVE-2020-11996 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-2020-11996?
CVE-2020-11996 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-2020-11996?
Run the dependency tree command: 'mvn dependency:tree -Dincludes=org.apache.tomcat'. 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-53hp-jpwq-2jgq",
  "modified" : "2026-06-11T14:28:00Z",
  "published" : "2022-02-09T23:01:22Z",
  "aliases" : [ "CVE-2020-11996" ],
  "summary" : "Uncontrolled Resource Consumption in Apache Tomcat",
  "details" : "A specially crafted sequence of HTTP/2 requests sent to Apache Tomcat 10.0.0-M1 to 10.0.0-M5, 9.0.0.M1 to 9.0.35 and 8.5.0 to 8.5.55 could trigger high CPU usage for several seconds. If a sufficient number of such requests were made on concurrent HTTP/2 connections, the server could become unresponsive.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
  } ],
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    },
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      } ]
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  "references" : [ {
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  }, {
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  }, {
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    "url" : "https://lists.debian.org/debian-lts-announce/2020/07/msg00010.html"
  }, {
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    "url" : "https://security.netapp.com/advisory/ntap-20200709-0002"
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    "url" : "https://usn.ubuntu.com/4596-1"
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    "url" : "http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00064.html"
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    "url" : "http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00072.html"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-400" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-04-12T19:42:18Z",
    "nvd_published_at" : "2020-06-26T17:15:00Z"
  }
}