How severe is CVE-2003-0866?

No CVSS score has been assigned to CVE-2003-0866 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2003-0866?

CVE-2003-0866 affects the following packages: org.apache.tomcat:tomcat (Maven). Ecosystems affected: Maven.

How do I fix CVE-2003-0866?

Update org.apache.tomcat:tomcat to 4.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2003-0866 is resolved across your whole dependency graph.

How do I detect CVE-2003-0866 in my Maven dependencies?

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.

How do I mitigate CVE-2003-0866 if there is no patch (or I can't update yet)?

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.

Is CVE-2003-0866 actively exploited in the wild?

Yes. There are 2 known exploit references for CVE-2003-0866, including 1 documented proof-of-concept exploit on Exploit-DB and 1 in-the-wild exploitation observed on GitHub and other sources. Treat this as actively exploitable and prioritize patching immediately. All exploit code should only be run in an isolated sandbox environment for research or authorized testing — never against production systems without explicit written authorization.

What is the EPSS score for CVE-2003-0866?

CVE-2003-0866 has an EPSS (Exploit Prediction Scoring System) score of 34.8%, placing it in the 98th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score warrants monitoring and prompt remediation.

When was CVE-2003-0866 published, and has it been updated?

CVE-2003-0866 was published on April 29, 2022 and was last updated on November 8, 2023. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

☕ Maven

Not in CISA KEV

CVE-2003-0866 — tomcat

CVE-2003-0866 is a security vulnerability in org.apache.tomcat:tomcat. 2 public exploit or proof-of-concept references are indexed, so weaponization risk is real. A fix is available for org.apache.tomcat:tomcat — see the affected versions and patch details below.

Apache Tomcat Denial of Service vulnerability in the Catalina package

Published

Apr 29, 2022

Updated

Nov 8, 2023

Affected

1 pkg

Patched

1 / 1

Exploits

2 known

Exploitation data as of Oct 19, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗

34.8%probability of exploitation in next 30 days

Moderate Risk0.00%

Lower risk than most CVEs98th percentile — riskier than 98% of all scored CVEsHighest risk

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

Real-World Exposure

1 pkg affected

☕org.apache.tomcat:tomcat

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

The Catalina org.apache.catalina.connector.http package in Tomcat 4.0.x up to 4.0.6 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.

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
☕Maven	`org.apache.tomcat:tomcat`	≥ 4.0&&< 4.1.0	4.1.0`org.apache.tomcat:tomcat:4.1.0`

Affected Products

1 product · 7 configurations

Application

tomcatapache

7 versions

4.0.04.0.14.0.24.0.34.0.44.0.54.0.6

Exploits & PoCs

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

EDB-23245doslinux✓ Verified

Apache Tomcat 4.0.x - Non-HTTP Request Denial of Service

by Oliver Karow · Oct 15, 2003

Exploit-DB Source

Detection & mitigation playbook

Open-source dependency

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.
Fix
Update org.apache.tomcat:tomcat to 4.1.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2003-0866 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.

Frequently Asked Questions

O3 Security · Impact-Aware SCA

Is CVE-2003-0866 in your dependencies?

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