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Apache Tomcat CVE-2026-77791

| EUVDEUVD-2026-85229 HIGH
Uncontrolled Resource Consumption (CWE-400)
2026-09-23 apache GHSA-9cg7-2q68-g3mq
Denial Of Service Apache Java Red Hat Tomcat Suse Apache Tomcat Apache Software Foundation
7.5
CVSS 3.1 · Vendor: apache
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Severity by source

Vendor (apache) PRIMARY
7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
vuln.today AI
5.3 MEDIUM

Network-reachable WebSocket endpoint, no auth or interaction implied, DoS-only with no C/I impact; A:L chosen conservatively as the advisory does not confirm complete resource exhaustion.

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

Primary rating from Vendor (apache).

CVSS VectorVendor: apache

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

Lifecycle Timeline

5
Re-analysis Queued
Sep 23, 2026 - 13:22 vuln.today
cvss_changed
CVSS changed
Sep 23, 2026 - 13:22 NVD
7.5 (HIGH)
Metadata Corrected
Sep 23, 2026 - 12:40 vuln.today
tag: Java added
Analysis Generated
Sep 23, 2026 - 12:15 vuln.today
CVE Published
Sep 23, 2026 - 11:20 cve.org
HIGH

DescriptionCVE.org

Uncontrolled Resource Consumption vulnerability in Apache Tomcat during sending of WebSocket close message enabled a DoS attack.

This issue affects Apache Tomcat: from 11.0.0-M5 through 11.0.25, from 10.1.8 through 10.1.59, from 9.0.74 through 9.0.121.

The following versions were EOL at the time the CVE was created but are known to be affected: from 8.5.88 through 8.5.100. Other unsupported versions may also be affected.

Users are recommended to upgrade to version 11.0.26, 10.1.60 or 9.0.122, which fix the issue.

AnalysisAI

Uncontrolled resource consumption in Apache Tomcat's WebSocket close-message handling allows unauthenticated remote attackers to exhaust server resources and degrade availability on instances that expose WebSocket endpoints. Per the assessed vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L), the impact is limited to availability (Low) with no confidentiality or integrity effect, and no user interaction is required. …

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Attack ChainAIDerived

Hypothetical attack flow derived from CVE metadata

Access
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Delivery
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Exploit
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Execution
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Vulnerability AssessmentAI

Exploitation Exploitation requires the target Tomcat instance to serve WebSocket connections and to reach the close-message sending path where resource consumption is uncontrolled; deployments not using WebSocket endpoints are not exposed. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment This is a CWE-400 uncontrolled-resource-consumption DoS in Apache Tomcat's WebSocket close-message handling, self-reported by the Apache Software Foundation. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in.
Exploit Scenario Full exploit scenario with step-by-step reproduction available after sign-in.
Remediation Vendor-released patch: upgrade to Apache Tomcat 11.0.26, 10.1.60, or 9.0.122 depending on your branch, as stated by the Apache Software Foundation advisory at https://lists.apache.org/thread/mb1pjjooqytrl6hbvbt3rw1lqwlon4cz. … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, inventory all Tomcat instances and identify those running the affected releases (11.0.0-M5 through 11.0.25, 10.1.8 through 10.1.59, 9.0.74 through 9.0.121, and 8.5.88 through 8.5.100), prioritizing internet-facing systems that serve WebSocket endpoints; enable monitoring and alerting on Tomcat thread-pool saturation, connection counts, and heap pressure, and apply connection-rate limits or WAF rules on WebSocket paths as a stopgap. …

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Vendor StatusVendor

SUSE

Severity: Important
Product Status
SUSE Linux Enterprise Desktop 15 SP7 SUSE Linux Enterprise Module for Basesystem 15 SP7 Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP4-LTSS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP5-ESPOS Fixed
SUSE Linux Enterprise High Performance Computing 15 SP5-LTSS Fixed

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CVE-2026-77791 vulnerability details – vuln.today
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