CVE-2021-42340 is a high-severity (CVSS 7.5) CWE-772 vulnerability in org.apache.tomcat:tomcat. EPSS puts its 30-day exploitation probability at 11.8% (96th percentile). A fix is available for org.apache.tomcat:tomcat — see the affected versions and patch details below.
Missing Release of Resource after Effective Lifetime in Apache Tomcat
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-42340 by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.
Where this sits among everything scored
Of 385,738 CVEs with a current EPSS score, this one falls in the 10–50% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcat☕org.apache.tomcat:tomcatReal-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
The fix for bug 63362 present in Apache Tomcat 10.1.0-M1 to 10.1.0-M5, 10.0.0-M1 to 10.0.11, 9.0.40 to 9.0.53 and 8.5.60 to 8.5.71 introduced a memory leak. The object introduced to collect metrics for HTTP upgrade connections was not released for WebSocket connections once the connection was closed. This created a memory leak that, over time, could lead to a denial of service via an OutOfMemoryError.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.tomcat:tomcat | ≥ 10.1.0-M1&&< 10.1.0-M6 | 10.1.0-M6org.apache.tomcat:tomcat:10.1.0-M6 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 10.0.0-M1&&< 10.0.12 | 10.0.12org.apache.tomcat:tomcat:10.0.12 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 9.0.40&&< 9.0.54 | 9.0.54org.apache.tomcat:tomcat:9.0.54 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 8.5.60&&< 8.5.72 | 8.5.72org.apache.tomcat:tomcat:8.5.72 |
Affected Products
tomcatapachedebian linuxdebianhcinetappmanagement services for element softwarenetappagile engineering data managementoraclebig data spatial and graphoracleDetection & mitigation playbook
Open-source dependencyDetect
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.
Fix
Update org.apache.tomcat:tomcat to 10.1.0-M6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-42340 is resolved across your whole dependency graph.
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.
Within Red Hat OpenStack Platform, Tomcat is provided as a component of OpenDaylight. This flaw will not receive a fix as OpenDaylight was deprecated as of OpenStack Platform 14 and is only receiving security fixes for Critical flaws. Red Hat Satellite does not include the affected Apache Tomcat, however, Tomcat is…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Enterprise Linux 9 | pki-servlet-engine-1:9.0.50-1.el9 | RHBA-2022:8077 |
| Red Hat Fuse 7.11 | tomcat | RHSA-2022:5532 |
| Red Hat JBoss Web Server 5 | tomcat | RHSA-2021:4863 |
| Red Hat JBoss Web Server 5.6 on RHEL 7 | jws5-tomcat-0:9.0.50-3.redhat_00004.1.el7jws | RHSA-2021:4861 |
| Red Hat Support for Spring Boot 2.5.10 | tomcat | RHSA-2022:1179 |
Frequently Asked Questions
Is CVE-2021-42340 in your dependencies?
Find it across Maven, including transitive dependencies.