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Apache Tomcat CVE-2026-86350

| EUVDEUVD-2026-85235 CRITICAL
HTTP Request/Response Smuggling (CWE-444)
2026-09-23 apache GHSA-6ff5-mwrj-376m
Apache Java Information Disclosure Red Hat Tomcat Request Smuggling Suse Apache Tomcat Apache Software Foundation
9.1
CVSS 3.1 · Vendor: apache
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Severity by source

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

Network-reachable and unauthenticated (AV:N/PR:N), but AC:H because reliably forcing an HTTP/2 concurrent-stream header mix-up needs timing/concurrency control; header leakage/misrouting gives C:L/I:L, no availability impact.

3.1 AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N
4.0 AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N
SUSE
7.7 HIGH
AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:L
Red Hat
7.2 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
High
Integrity
High
Availability
None

Lifecycle Timeline

3
Metadata Corrected
Sep 23, 2026 - 12:40 vuln.today
tag: Java added
Analysis Generated
Sep 23, 2026 - 12:17 vuln.today
CVE Published
Sep 23, 2026 - 11:31 cve.org
HIGH

DescriptionCVE.org

Inconsistent interpretation of HTTP/2 requests ('HTTP Request/Response smuggling') vulnerability in Apache Tomcat caused by a regression in fix for CVE-2026-41293 can trigger request header mix-up.

This issue affects Apache Tomcat: from 11.0.22 through 11.0.25, from 10.1.55 through 10.1.59, from 9.0.118 through 9.0.121.

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

Articles & Coverage 1

News Critical HTTP/2 Request Smuggling in Apache Tomcat - CVE-2026-86350 Sep 23, 2026

AnalysisAI

HTTP/2 request smuggling in Apache Tomcat can mix up request headers between concurrent streams, allowing unauthenticated remote attackers to potentially read or alter other users' request data when the connector has HTTP/2 explicitly enabled. The flaw is a regression from the fix for CVE-2026-41293 and affects only Tomcat 11.0.22 through 11.0.25, 10.1.55 through 10.1.59, and 9.0.118 through 9.0.121; exploitation is rated high complexity (AC:H) with limited confidentiality and integrity impact (C:L/I:L). …

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Attack ChainAIDerived

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Vulnerability AssessmentAI

Exploitation Requires the target Tomcat connector to have HTTP/2 enabled - in Tomcat this is not on by default and must be explicitly configured via an UpgradeProtocol element (org.apache.coyote.http2.Http2Protocol) on the connector. … Additional conditions and limiting factors are described in the full assessment.
Risk Assessment This is a genuine, exploitable protocol-layer flaw but a moderate priority rather than a critical emergency. … 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, which fix the issue (see the advisory at https://lists.apache.org/thread/mss45z99lcdd5dtpgcn45dy82f3toswc). … Detailed patch versions, workarounds, and compensating controls in full report.
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Recommended ActionAI

Within 24 hours, inventory every Apache Tomcat instance and determine which ones run 11.0.22-11.0.25, 10.1.55-10.1.59, or 9.0.118-9.0.121, and for each confirm whether the HTTP/2 connector is explicitly enabled; where HTTP/2 is not a hard business requirement, disable it immediately (remove the HTTP/2 UpgradeProtocol/Connector configuration and revert to HTTP/1.1), which removes exposure entirely without a code change. …

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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-2026-86350 vulnerability details – vuln.today
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