# CVE-2019-0199: Apache Tomcat Denial of Service in HTTP/2 implementation

Source: https://junglewise.ai/threats/cve-2019-0199-apache-tomcat-denial-of-service-in-http-2-implementation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2020-06-15. Updated: 2026-05-20  
License: CC BY 4.0 with a link back

CVE-2019-0199 · Severity: high · CVSS 7.5 · Published 2020-06-15

Apache Tomcat is a widely used web server for hosting Java-based applications. A flaw in its handling of modern web traffic (HTTP/2) allows an attacker to overwhelm the server by keeping connections open without sending data. This can lead to a complete service outage, preventing legitimate users from accessing hosted applications.

Technologies: [Apache Tomcat](https://junglewise.ai/threats/technologies/tomcat), [org.apache.tomcat:tomcat-coyote (Maven)](https://junglewise.ai/threats/technologies/org-apache-tomcat-tomcat-coyote), [org.apache.tomcat.embed:tomcat-embed-core (Maven)](https://junglewise.ai/threats/technologies/org-apache-tomcat-embed-tomcat-embed-core). Vendors: [Apache](https://junglewise.ai/threats/vendors/apache), [Maven](https://junglewise.ai/threats/vendors/maven).

## Quick answers

**Is CVE-2019-0199 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2019-0199 being exploited in the wild.

**How severe is CVE-2019-0199?** High severity, with a CVSS score of 7.5, published 15 June 2020.

**Which products and versions are affected?** Apache Tomcat 9.0.0.M1 to 9.0.14, 8.5.0 to 8.5.37; org.apache.tomcat:tomcat-coyote (Maven) ECOSYSTEM:introduced=9.0.0,fixed=9.0.16; org.apache.tomcat.embed:tomcat-embed-core (Maven) ECOSYSTEM:introduced=9.0.0,fixed=9.0.16.

**Is there a fix for CVE-2019-0199?** Yes. org.apache.tomcat:tomcat-coyote (Maven): upgrade to 9.0.16 or later; org.apache.tomcat.embed:tomcat-embed-core (Maven): upgrade to 9.0.16 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2019-0199 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2019-0199?** Check whether you run Apache Tomcat, org.apache.tomcat:tomcat-coyote (Maven) or org.apache.tomcat.embed:tomcat-embed-core (Maven) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- org.apache.tomcat:tomcat-coyote (Maven): upgrade to 9.0.16 or later

  ```sh
  # set org.apache.tomcat:tomcat-coyote to 9.0.16 in your pom.xml or build.gradle
  ```

- org.apache.tomcat.embed:tomcat-embed-core (Maven): upgrade to 9.0.16 or later

  ```sh
  # set org.apache.tomcat.embed:tomcat-embed-core to 9.0.16 in your pom.xml or build.gradle
  ```


## Technical details

The HTTP/2 implementation in Apache Tomcat fails to properly limit the number of SETTINGS frames and allows clients to maintain open streams without active data transfer. By exploiting the Servlet API's blocking I/O, a remote attacker can keep these streams open indefinitely, eventually exhausting the server's thread pool. This results in a Denial of Service (DoS) condition where the server can no longer process new requests. The vulnerability is patched in versions 9.0.16 and 8.5.38.

## Affected products

- Apache Tomcat 9.0.0.M1 to 9.0.14, 8.5.0 to 8.5.37

## Identifiers

- CVE-2019-0199
- GHSA-qcxh-w3j9-58qr

## Timeline

- 2019-04-10: advisory: NVD publication date
- 2020-06-15: disclosed: GitHub Advisory published

## References

- [https://api.github.com/users/aruneko](https://api.github.com/users/aruneko)
- [https://github.com/aruneko](https://github.com/aruneko)
- [https://api.github.com/users/aruneko/gists%7B/gist_id%7D](https://api.github.com/users/aruneko/gists%7B/gist_id%7D)
- [https://api.github.com/users/aruneko/repos](https://api.github.com/users/aruneko/repos)
- [https://avatars.githubusercontent.com/u/2957726?v=4](https://avatars.githubusercontent.com/u/2957726?v=4)
- [https://api.github.com/users/aruneko/events%7B/privacy%7D](https://api.github.com/users/aruneko/events%7B/privacy%7D)

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