High severity · published Sep 23, 2026
CVE-2026-78437
Apache Tomcat: HTTP/2 DoS via malformed request
7.3
CVSS
0.5%
EPSS
No
On KEV
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.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
Low
Integrity
Low
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 43% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
TO
Tomcat · Apache
11.0.19 through 11.0.25; 10.1.53 through 10.1.59; 9.0.116 through 9.0.121 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-78437
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-78437
lists.apache.org
https://lists.apache.org/thread/qkmsos3s8chn5053qr466rzwv6sk5gjg
www.openwall.com
http://www.openwall.com/lists/oss-security/2026/09/23/26
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