CVE-2003-0866 Apache Tomcat Denial of Service vulnerability in the Catalina package

What is CVE-2003-0866?

CVE-2003-0866 is a medium-severity denial of service vulnerability in Apache Tomcat, published on 17 Oct 2003. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

The Catalina org.apache.catalina.connector.http package in Tomcat 4.0.x up to 4.0.3 allows remote attackers to cause a denial of service via several requests that do not follow the HTTP protocol, which causes Tomcat to reject later requests.

Which versions are affected by CVE-2003-0866?

2 open source packages ship an affected version, including org.apache.tomcat:tomcat. It affects 1 product.

Products include Apache Tomcat.

How do I fix CVE-2003-0866?

Upgrade org.apache.tomcat:tomcat to 4.1.0 or later.

Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.

Is CVE-2003-0866 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2003-0866 exists.

Public exploit code: 1 Exploit-DB entry.

Other vulnerabilities in Apache Tomcat

• CVE-2025-24813 Apache Tomcat Path Equivalence Exploited Critical 10.0
• CVE-2016-8735 Apache Tomcat Remote Code Execution Exploited Critical 9.8
• CVE-2017-12617 Apache Tomcat Remote Code Execution Exploited High 8.1
• CVE-2017-12615 Apache Tomcat on Windows Remote Code Execution Exploited High 8.1
• CVE-2026-34486 Apache Tomcat Missing Encryption of Sensitive Data Exploited High 7.5

All Apache Tomcat vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DSA-395, GHSA-7wj2-48c4-2684.