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

Severity: high (CVSS 7.3 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-23 · updated 2026-09-23
Weakness: CWE-459

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 products

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

References

https://lists.apache.org/thread/qkmsos3s8chn5053qr466rzwv6sk5gjg
http://www.openwall.com/lists/oss-security/2026/09/23/26

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