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Vulnerability · Published Sep 23, 2026 · Assigned by apache

CVE-2026-78437Apache Tomcat: HTTP/2 DoS via malformed request

High 7.3

In plain English

A high-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 44% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)7.3High
Exploit odds (30 days)0.5%top 56.2% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official description

Incomplete cleanup vulnerability in Apache Tomcat allows a malformed request to potentially (depends on timing) cause one request from another user to fail. This issue affects Apache Tomcat: from 11.0.19 through 11.0.25, from 10.1.53 through 10.1.59, from 9.0.116 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-2026-78437
Debian:13tomcat10no fix listedDEBIAN-CVE-2026-78437
Debian:14tomcat1010.1.60-1DEBIAN-CVE-2026-78437
Debian:13tomcat11no fix listedDEBIAN-CVE-2026-78437
Debian:14tomcat11no fix listedDEBIAN-CVE-2026-78437
Debian:12tomcat99.0.70-2DEBIAN-CVE-2026-78437
Debian:13tomcat99.0.70-2DEBIAN-CVE-2026-78437
Debian:14tomcat99.0.70-2DEBIAN-CVE-2026-78437
Ubuntu:24.04:LTStomcat10no fix listedUBUNTU-CVE-2026-78437
Ubuntu:26.04:LTStomcat10no fix listedUBUNTU-CVE-2026-78437
Ubuntu:26.10tomcat10no fix listedUBUNTU-CVE-2026-78437
Ubuntu:26.04:LTStomcat11no fix listedUBUNTU-CVE-2026-78437
Ubuntu:26.10tomcat11no fix listedUBUNTU-CVE-2026-78437
Ubuntu:24.04:LTStomcat9no fix listedUBUNTU-CVE-2026-78437
Ubuntu:26.04:LTStomcat9no fix listedUBUNTU-CVE-2026-78437
Ubuntu:26.10tomcat9no fix listedUBUNTU-CVE-2026-78437

Affected products (as reported)

VendorProductVersions
Apache Software Foundation Apache Tomcat 11.0.19 – through 11.0.2510.1.53 – through 10.1.599.0.116 – through 9.0.121

Weakness: CWE-459 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L

References