CVE-2026-86350
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HTTP Request Smuggling in Apache Tomcat

Publication date: 2026-09-23

Last updated on: 2026-09-23

Assigner: Apache Software Foundation

Description
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.

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Meta Information

Published
2026-09-23
Last Modified
2026-09-23
Generated
2026-09-24
AI Q&A
2026-09-23
EPSS Evaluated
N/A
NVD
CVE-2026-86350
EUVD
EUVD-2026-85235

Affected Vendors & Products

Showing 6 associated CPEs
Vendor Product Version / Range
apache tomcat From 11.0.22 (inc) to 11.0.25 (inc)
apache tomcat From 10.1.55 (inc) to 10.1.59 (inc)
apache tomcat From 9.0.118 (inc) to 9.0.121 (inc)
apache tomcat 11.0.26
apache tomcat 10.1.60
apache tomcat 9.0.122

Helpful Resources

Exploitability

CWE
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KEV
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CWE ID Description
CWE-444 The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.

Attack-Flow Graph

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Executive Summary

This vulnerability is a regression in Apache Tomcat that allows HTTP request/response smuggling due to inconsistent interpretation of HTTP/2 requests. It causes request header mix-ups, potentially leading to security bypasses or data leaks.

Detection Guidance

Detection involves checking Apache Tomcat versions affected by CVE-2026-86350. Verify if your Tomcat version falls within 11.0.22-11.0.25, 10.1.55-10.1.59, or 9.0.118-9.0.121. Use commands like 'catalina.sh version' or check server logs for version details.

Impact Analysis

An attacker could exploit this to manipulate requests, bypass security controls, or access unauthorized data. Systems running affected Tomcat versions may experience misrouted requests or incorrect responses.

Compliance Impact

This vulnerability could lead to unauthorized data access or breaches, violating GDPR (data protection) and HIPAA (health data privacy). Non-compliance risks fines or legal penalties due to compromised data integrity.

Mitigation Strategies

Upgrade Apache Tomcat to version 11.0.26, 10.1.60, or 9.0.122 or later to resolve the issue.

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