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Medium severity · published Jul 28, 2026
CVE-2026-66299
Apache Tomcat: DoS via WebSocket chat example
5.3
CVSS
0.6%
EPSS
No
On KEV
Description
Uncontrolled Resource Consumption vulnerability in Apache Tomcat's WebSocket chat example. This issue affects Apache Tomcat: from 11.0.0-M20 through 11.0.24, from 10.1.24 through 10.1.57, from 9.0.89 through 9.0.120. Users who have followed the security guidance to remove the examples web application are not affected by this issue. Users are recommended to remove the examples web application or to upgrade to version 11.0.25, 10.1.58 or 9.0.121 (when released), which fix the issue.
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.6% · higher than 46% 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-M20 through 11.0.24; 10.1.24 through 10.1.57; 9.0.89 through 9.0.120 · source: vendor, NVD
Affected product
TO
Tomcat
Apache
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-66299
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-66299
Mailing List
https://lists.apache.org/thread/8owczcc1o8qw1rxmg9gvfk4w2jnh4l5k
Mailing List
http://www.openwall.com/lists/oss-security/2026/07/28/25
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