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Apache Tomcat CVE-2026-66299

| EUVDEUVD-2026-49855 MEDIUM
Uncontrolled Resource Consumption (CWE-400)
2026-07-28 apache GHSA-rpf9-hrjr-88fv
Denial Of Service Apache Tomcat Apache Tomcat Apache Software Foundation
Medium
Disputed · 5.3 NVD
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Severity by source

Sources disagree (Low–High)
Vendor (apache) PRIMARY
LOW
qualitative
NVD
5.3 MEDIUM
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
vuln.today AI
7.5 HIGH

Network‑reachable example with no authentication; only availability impact from resource exhaustion.

3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
4.0 AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N
SUSE
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Red Hat
5.3 MEDIUM
qualitative

vuln.today treats the vendor’s rating as authoritative. A higher third-party CVSS (e.g. CISA-ADP) is shown for transparency but does not drive the headline severity.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
Low

Lifecycle Timeline

5
Severity Changed
Aug 27, 2026 - 16:37 NVD
HIGH MEDIUM
CVSS changed
Aug 27, 2026 - 16:37 NVD
7.5 (HIGH) 5.3 (MEDIUM)
CVSS changed
Jul 28, 2026 - 18:22 NVD
7.5 (HIGH)
Analysis Generated
Jul 28, 2026 - 15:19 vuln.today
CVE Published
Jul 28, 2026 - 14:29 cve.org
LOW

DescriptionNVD

Uncontrolled Resource Consumption vulnerability in Apache Tomcat's WebSocket chat example.

This issue affects Apache Tomcat: from 11.0.0-M20 through 11.0.24, from 10.1.24 through 10.1.57, from 9.0.89 through 9.0.120. Users who have followed the security guidance to remove the examples web application are not affected by this issue.

Users are recommended to remove the examples web application or to upgrade to version 11.0.25, 10.1.58 or 9.0.121 (when released), which fix the issue.

Articles & Coverage 1

News 4 New Apache Vulnerabilities - 1 Critical, 3 High Jul 29, 2026

AnalysisAI

Uncontrolled resource consumption in Apache Tomcat's default WebSocket chat example allows remote attackers to cause denial of service. Affected versions include 11.0.0-M20 through 11.0.24, 10.1.24 through 10.1.57, and 9.0.89 through 9.0.120; users who have removed the examples web application as recommended are not impacted. No public exploit code or active exploitation is reported.

Technical ContextAI

The vulnerability exists in the WebSocket chat example bundled with Apache Tomcat, which implements real‑time messaging using the Java WebSocket API (JSR 356). CWE‑400 (Uncontrolled Resource Consumption) indicates that the example fails to properly limit resource allocation when handling certain inputs, allowing an attacker to exhaust server resources. CPE cpe:2.3:a:apache_software_foundation:apache_tomcat:*:*:*:*:*:*:*:* confirms that all Tomcat instances within the stated version ranges are affected if the examples webapp is present. The root cause is a lack of rate‑limiting or input validation in the demo application, not in the core Tomcat container.

RemediationAI

The primary remediation is to remove the examples web application from the Tomcat installation, which is already recommended in the security guidance for production deployments. If removal is not immediately possible, upgrading to Apache Tomcat 11.0.25, 10.1.58, or 9.0.121 (once released) eliminates the vulnerability. No runtime workarounds are provided; blocking access to the /examples/websocket/chat path via a reverse proxy or firewall can serve as a temporary compensating control, but complete removal is the only certain fix.

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Same weakness CWE-400 – Uncontrolled Resource Consumption

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Same technique Denial Of Service

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise High Performance Computing 15 SP7 Affected
SUSE Linux Enterprise Module for Web and Scripting 15 SP7 Affected
SUSE Linux Enterprise Module for Web and Scripting 15 SP7 Affected

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CVE-2026-66299 vulnerability details – vuln.today
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