High severity · published Sep 23, 2026
CVE-2026-77791
Apache Tomcat: DoS via busy wait during WebSocket close
7.5
CVSS
0.7%
EPSS
No
On KEV
Description
Uncontrolled Resource Consumption vulnerability in Apache Tomcat during sending of WebSocket close message enabled a DoS attack.
This issue affects Apache Tomcat: from 11.0.0-M5 through 11.0.25, from 10.1.8 through 10.1.59, from 9.0.74 through 9.0.121.
The following versions were EOL at the time the CVE was created but are
known to be affected: from 8.5.88 through 8.5.100. Other unsupported versions may also be affected.
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:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.7% · higher than 52% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
TO
Tomcat · Apache
11.0.0-M5 through 11.0.25; 10.1.8 through 10.1.59; 9.0.74 through 9.0.121; 8.5.88 through 8.5.100 · source: vendor
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-77791
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-77791
lists.apache.org
https://lists.apache.org/thread/mb1pjjooqytrl6hbvbt3rw1lqwlon4cz
www.openwall.com
http://www.openwall.com/lists/oss-security/2026/09/23/24
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