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Vulnerability · Published Sep 23, 2026 · Assigned by apache

CVE-2026-86350Apache Tomcat: Regression in fix for CVE-2026-41293 can trigger request header mix-up

Critical 9.1

In plain English

A critical-severity security flaw in Apache Tomcat from Apache Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.5% (higher than 42% of all known vulnerabilities). Ready-made attack tooling exists: public proof-of-concept code. Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)9.1Critical
Exploit odds (30 days)0.5%top 58.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack tooling1Public PoC

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Debian:12tomcat10no fix listedDEBIAN-CVE-2026-86350
Debian:13tomcat10no fix listedDEBIAN-CVE-2026-86350
Debian:14tomcat1010.1.60-1DEBIAN-CVE-2026-86350
Debian:13tomcat11no fix listedDEBIAN-CVE-2026-86350
Debian:14tomcat11no fix listedDEBIAN-CVE-2026-86350
Debian:12tomcat99.0.70-2DEBIAN-CVE-2026-86350
Debian:13tomcat99.0.70-2DEBIAN-CVE-2026-86350
Debian:14tomcat99.0.70-2DEBIAN-CVE-2026-86350
Ubuntu:24.04:LTStomcat10no fix listedUBUNTU-CVE-2026-86350
Ubuntu:26.04:LTStomcat10no fix listedUBUNTU-CVE-2026-86350
Ubuntu:26.10tomcat10no fix listedUBUNTU-CVE-2026-86350
Ubuntu:26.04:LTStomcat11no fix listedUBUNTU-CVE-2026-86350
Ubuntu:26.10tomcat11no fix listedUBUNTU-CVE-2026-86350
Ubuntu:24.04:LTStomcat9no fix listedUBUNTU-CVE-2026-86350
Ubuntu:26.04:LTStomcat9no fix listedUBUNTU-CVE-2026-86350
Ubuntu:26.10tomcat9no fix listedUBUNTU-CVE-2026-86350

Affected products (as reported)

VendorProductVersions
Apache Software Foundation Apache Tomcat 11.0.22 – through 11.0.2510.1.55 – through 10.1.599.0.118 – through 9.0.121

Weakness: CWE-444 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

References