GHSA-53hp-jpwq-2jgq BIT-tomcat-2020-11996 CVE-2020-11996

Uncontrolled Resource Consumption in Apache Tomcat

High Maven

Severity: 7.5 / 10; High · CVSS 3.1
Exploit chance (EPSS): 26.70%; Chance of exploitation in the next 30 days. Higher than 98.03% of scored vulnerabilities.
Known exploited: No; Not in CISA's catalog
Weakness: CWE-400 Uncontrolled Resource Consumption
Fix: Available; 2 packages have a fixed version

Description

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.

Affected versions

Maven

Package	Vulnerable	Fixed in
org.apache.tomcat.embed:tomcat-embed-core	`>= 10.0.0-M1, < 10.0.0-M5`	`10.0.0-M5`
org.apache.tomcat.embed:tomcat-embed-core	`>= 9.0.0.M1, < 9.0.35`	`9.0.35`
org.apache.tomcat.embed:tomcat-embed-core	`>= 8.5.0, < 8.5.55`	`8.5.55`
org.apache.tomcat:tomcat	`>= 10.0.0-M1, < 10.0.0-M5`	`10.0.0-M5`
org.apache.tomcat:tomcat	`>= 9.0.0.M1, < 9.0.35`	`9.0.35`
org.apache.tomcat:tomcat	`>= 8.5.0, < 8.5.55`	`8.5.55`

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

org.apache.tomcat.embed:tomcat-embed-core Maven → `10.0.0-M5`

maven

<dependency><groupId>org.apache.tomcat.embed</groupId><artifactId>tomcat-embed-core</artifactId><version>10.0.0-M5</version></dependency>

gradle

implementation("org.apache.tomcat.embed:tomcat-embed-core:10.0.0-M5")

org.apache.tomcat:tomcat Maven → `10.0.0-M5`

maven

<dependency><groupId>org.apache.tomcat</groupId><artifactId>tomcat</artifactId><version>10.0.0-M5</version></dependency>

gradle

implementation("org.apache.tomcat:tomcat:10.0.0-M5")

Severity breakdown

CVSS 3.1 7.5

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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

Weakness

CWE-400: Uncontrolled Resource Consumption

The product does not properly control the allocation and maintenance of a limited resource.

How to prevent it

Architecture and Design: Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place. The login application should be protected against DoS attacks as much as possible. Limiting the database access, perhaps by caching result sets, can help minimize the resources expended. To further limit the potential for a DoS attack, consider tracking the rate of requests received from users and blocking requests that exceed a defined rate threshold.
Architecture and Design: Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed. The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question. The second solution is simply difficult to effectively institute -- and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.
Architecture and Design: Ensure that protocols have specific limits of scale placed on them.
Implementation: Ensure that all failures in resource allocation place the system into a safe posture.

References

Advisories

nvd.nist.gov/vuln/detail/CVE-2020-11996

Packages

github.com/apache/tomcat

Timeline

Feb 9, 2022 Published
Jun 11, 2026 Last updated by the source
Oct 31, 2026 Latest EPSS score

Advisory	Severity	Why it's related
GHSA-69r9-qgr7-g2wj Apache Tomcat Missing Encryption of Sensitive Data vulnerability	High Known exploited	Also affects org.apache.tomcat:tomcat
GHSA-83qj-6fr2-vhqg Apache Tomcat: Potential RCE and/or information disclosure and/or information corruption with partial PUT	Critical Known exploited	Also affects org.apache.tomcat.embed:tomcat-embed-core
GHSA-qppj-fm5r-hxr3 HTTP/2 Stream Cancellation Attack	Medium Known exploited	Also affects org.apache.tomcat.embed:tomcat-embed-core
GHSA-xjgh-84hx-56c5 Unrestricted Upload of File with Dangerous Type Apache Tomcat	High Known exploited	Also affects org.apache.tomcat.embed:tomcat-embed-core
CVE-2020-1938 Improper Privilege Management in Tomcat	Critical Known exploited	Also affects org.apache.tomcat.embed:tomcat-embed-core
GHSA-pjfr-qf3p-3q25 When running Apache Tomcat on Windows with HTTP PUTs enabled it was possible to upload a JSP file to the server	High Known exploited	Also affects org.apache.tomcat.embed:tomcat-embed-core
GHSA-h3x4-894j-xpx5 Apache Tomcat's FORM authentication process has an Incorrect Authorization vulnerability	Critical	Also affects org.apache.tomcat.embed:tomcat-embed-core
GHSA-9xv2-5v5q-p794 Apache Tomcat's DIGEST authenticator has an Authentication Bypass by Capture-replay vulnerability	Critical	Also affects org.apache.tomcat.embed:tomcat-embed-core

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