Resource exhaustion in Apache Software Foundation Tomcat

CVE-2026-77791

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.

Vulnerability class: DoS (Denial of Service)

Published · last modified .

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.007 (52.4th percentile), scored .

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 52nd percentile — 52.4% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS trend (30 days)EPSS over the last 30 days for CVE-2026-77791: held from 0.005 to 0.007.

EPSS over last 30 days · oldest: 0.005 · newest: 0.007 · change: +0.001

Affected products

Weakness classification (CWE)

References

Frequently asked questions

What is CVE-2026-77791?
CVE-2026-77791 is a high-severity vulnerability in Apache Software Foundation Tomcat, classified under Uncontrolled Resource Consumption. CVSS score: 7.5/10. Published 2026-09-23.
How severe is CVE-2026-77791?
High severity. CVSS v3 base score is 7.5 out of 10.