CVE-2021-41079 is a high-severity (CVSS 7.5) Improper Input Validation vulnerability in org.apache.tomcat:tomcat. A fix is available for org.apache.tomcat:tomcat — see the affected versions and patch details below.
Infinite loop in Tomcat due to parsing error
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
CVE-2021-41079 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% band (highlighted). Counts from FIRST.org, log-scaled.
Real-World Exposure
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
Apache Tomcat 8.5.0 to 8.5.63, 9.0.0-M1 to 9.0.43 and 10.0.0-M1 to 10.0.2 did not properly validate incoming TLS packets. When Tomcat was configured to use NIO+OpenSSL or NIO2+OpenSSL for TLS, a specially crafted packet could be used to trigger an infinite loop resulting in a denial of service.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.apache.tomcat:tomcat | ≥ 10.0.0&&< 10.0.4 | 10.0.4org.apache.tomcat:tomcat:10.0.4 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 9.0.0&&< 9.0.44 | 9.0.44org.apache.tomcat:tomcat:9.0.44 |
| ☕Maven | org.apache.tomcat:tomcat | ≥ 8.5.0&&< 8.5.64 | 8.5.64org.apache.tomcat:tomcat:8.5.64 |
Affected Products
tomcatapachedebian linuxdebianmanagement services for element software and netapp hcinetappDetection & 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 10.0.4 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2021-41079 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.
In Red Hat Certificate System versions 9 and older, the version of Tomcat used is not affected by this flaw. In Red Hat Certificate System 10, Tomcat is affected by this flaw. However, Tomcat is configured so that it does not use OpenSSLEngine, but the Dogtag JSS SSL implementation. As a result, the flaw can not be…
| Product | Fixed in | Advisory |
|---|---|---|
| Red Hat Fuse 7.11 | tomcat | RHSA-2022:5532 |
| Red Hat JBoss Web Server 5 | see advisory | RHSA-2021:3743 |
| Red Hat JBoss Web Server 5.5 on RHEL 7 | jws5-tomcat-0:9.0.43-13.redhat_00013.1.el7jws | RHSA-2021:3741 |
| Red Hat Support for Spring Boot 2.5.10 | tomcat | RHSA-2022:1179 |
Frequently Asked Questions
Is CVE-2021-41079 in your dependencies?
Find it across Maven, including transitive dependencies.