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HIGH severity

CVE-2020-13934 — tomcat

HIGH

CVE-2020-13934 is a high-severity (CVSS 7.5) CWE-401 vulnerability in org.apache.tomcat:tomcat. EPSS puts its 30-day exploitation probability at 64.1% (99th percentile). A fix is available for org.apache.tomcat:tomcat — see the affected versions and patch details below.

Improper Restriction of Operations within the Bounds of a Memory Buffer in Apache Tomcat

Also known asBIT-tomcat-2020-13934GHSA-vf77-8h7g-gghp
Published
Updated
Affected
6 pkgs
Patched
6 / 6
Exploits
None indexed
Exploitation data as of Oct 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

No confirmed exploitation observed yet

  • CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
  • CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2020-13934.

EPSS Exploitation Probability

via FIRST.org ↗
64.1%probability of exploitation in next 30 days
High Risk0.00%
Lower risk than most CVEs99th percentile — riskier than 99% of all scored CVEsHighest risk
11.2%32.9%54.6%76.3%23.4%64.1%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

CVE-2020-13934 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 385,987 CVEs with a current EPSS score, this one falls in the 50–90% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

6 pkgs affected
☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote☕org.apache.tomcat:tomcat-coyote

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

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.

Affected Packages

6 total 6 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.apache.tomcat:tomcat≥ 10.0.0-M1&&< 10.0.0-M610.0.0-M6org.apache.tomcat:tomcat:10.0.0-M6
☕Mavenorg.apache.tomcat:tomcat≥ 9.0.0.M5&&< 9.0.369.0.36org.apache.tomcat:tomcat:9.0.36
☕Mavenorg.apache.tomcat:tomcat≥ 8.5.1&&< 8.5.568.5.56org.apache.tomcat:tomcat:8.5.56
☕Mavenorg.apache.tomcat:tomcat-coyote≥ 10.0.0-M1&&< 10.0.0-M610.0.0-M6org.apache.tomcat:tomcat-coyote:10.0.0-M6
☕Mavenorg.apache.tomcat:tomcat-coyote≥ 9.0.0.M5&&< 9.0.369.0.36org.apache.tomcat:tomcat-coyote:9.0.36
☕Mavenorg.apache.tomcat:tomcat-coyote≥ 8.5.1&&< 8.5.568.5.56org.apache.tomcat:tomcat-coyote:8.5.56

Affected Products

14 products · 54 configurations
Application
tomcatapache
≥ 9.0.1 && ≤ 9.0.36
2 versions
9.0.010.0.0
OS
ubuntu linuxcanonical
1 version
20.04
OS
debian linuxdebian
2 versions
9.010.0
Application
oncommand system managernetapp
≥ 3.0.0 && ≤ 3.1.3
range
OS
leapopensuse
2 versions
15.115.2
Application
agile engineering data managementoracle
1 version
6.2.1.0

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.tomcat:tomcat, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.apache.tomcat:tomcat to 10.0.0-M6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-13934 is resolved across your whole dependency graph.

  3. Workarounds

    Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant

Red Hat Certificate System 10.0 and Red Hat Enterprise Linux 8's Identity Management, are using a vulnerable version of Tomcat that is bundled into the pki-servlet-engine component. However, HTTP/2 is not enabled in such a configuration, and it is not possible to trigger the flaw in a supported setup. A future update…

ProductFixed inAdvisory
Red Hat Fuse 7.9tomcatRHSA-2021:3140
Red Hat JBoss Web Server 5.3 on RHEL 6jws5-tomcat-0:9.0.30-5.redhat_6.1.el6jwsRHSA-2020:3306
Red Hat JBoss Web Server (JWS) 5.3tomcatRHSA-2020:3308
Red Hat Runtimes Spring Boot 2.2.6tomcatRHSA-2020:3806

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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CVE-2020-13934: tomcat DoS — Fixed in 10.0.0-M6