---
title: "CVE-2020-13943: Apache Tomcat vulnerability | CubePath"
description: "If an HTTP/2 client connecting to Apache Tomcat 10.0.0-M1 to 10.0.0-M7, 9.0.0.M1 to 9.0.37 or 8.5.0 to 8.5.57 exceeded the agreed maximum number…"
language: en
source: https://cubepath.com/security/cve/CVE-2020-13943
---

# CVE-2020-13943: Apache Tomcat vulnerability | CubePath

## Description

If an HTTP/2 client connecting to Apache Tomcat 10.0.0-M1 to 10.0.0-M7, 9.0.0.M1 to 9.0.37 or 8.5.0 to 8.5.57 exceeded the agreed maximum number of concurrent streams for a connection (in violation of the HTTP/2 protocol), it was possible that a subsequent request made on that connection could contain HTTP headers - including HTTP/2 pseudo headers - from a previous request rather than the intended headers. This could lead to users seeing responses for unexpected resources.

Official description from the CVE record, published by apache. Copyright © 1999-2026 The MITRE Corporation. See [/security/cve/legal](https://cubepath.com/security/cve/legal) for the CVE license. [View the record on cve.org](https://www.cve.org/CVERecord?id=CVE-2020-13943)

## Key data

### EPSS

Exploit Prediction Scoring System by FIRST: an estimate of the probability that exploitation activity will be observed in the next 30 days.

Score

0.52639 (52.6% probability)

Percentile

99.0%

Scores of

Nov 10, 2026

Model

v2026.06.15

### CISA assessment as of Oct 8, 2026

Stakeholder-Specific Vulnerability Categorization (SSVC) decision points added by CISA.

Automatable

yes

Technical impact

partial

## Affected products

Products listed in the CVE record, as the CNA published them.

- Apache Tomcat

  - affected: Apache Tomcat 10.0.0-M1 to 10.0.0-M7, 9.0.0.M1 to 9.0.37, 8.5.0 to 8.5.57

## References

Links listed in the CVE record. They lead to other sites, which CubePath does not control.

- [lists.apache.org/thread.html/r4a390027eb27e4550142fac6c8317…](https://lists.apache.org/thread.html/r4a390027eb27e4550142fac6c8317cc684b157ae314d31514747f307%40%3Cannounce.tomcat.apache.org%3E)
- [\[debian-lts-announce\] 20201014 \[SECURITY\] \[DLA 2407-1\] tomcat8 security update](https://lists.debian.org/debian-lts-announce/2020/10/msg00019.html)  (lists.debian.org) mailing-list
- [openSUSE-SU-2020:1799](http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00002.html)  (lists.opensuse.org) vendor-advisory
- [openSUSE-SU-2020:1842](http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00021.html)  (lists.opensuse.org) vendor-advisory
- [DSA-4835](https://www.debian.org/security/2021/dsa-4835)  (debian.org) vendor-advisory
- [oracle.com/security-alerts/cpuApr2021.html](https://www.oracle.com/security-alerts/cpuApr2021.html)
- [security.netapp.com/advisory/ntap-20201016-0007](https://security.netapp.com/advisory/ntap-20201016-0007/)

## Timeline

1. ID reserved Jun 8, 2020
2. Record published Oct 12, 2020
3. Record last updated Oct 8, 2026

## Look up another CVE

## About CubePath

CubePath is a cloud provider with data centers in Europe and the United States. It offers VPS, bare metal servers and DDoS protection.

[Cloud VPS](https://cubepath.com/vps) [DDoS protection](https://cubepath.com/ddos-protection)

Data from the CVE Program (MITRE), CISA KEV and FIRST EPSS. CVSS is owned by FIRST and used by permission. Not affiliated with or endorsed by MITRE, CISA or FIRST. Data as of Nov 10, 2026, 20:05 UTC. [Sources and licenses](https://cubepath.com/security/cve/legal)