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Fencer Vulns
high 7.5

CVE-2026-66299 json

Apache Tomcat: DoS via WebSocket chat example

published 2026-07-28 3 mo ago modified 2026-10-24 15 d ago also BIT-tomcat-2026-66299 , EUVD-2026-49855

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 46%
public exploits
0
none known

Summary

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.

Patch / fix

  • bitnami tomcat 9.0.121, 10.1.58, 11.0.25
  • tomcat9 Debian 14, Debian 13, Debian 12 9.0.70-2
  • tomcat10 Debian 14 10.1.60-1

debian advisories DEBIAN-CVE-2026-66299

  • jws7-tomcat jboss enterprise web server 7.0 11.0.21-7.redhat_00006.1.el10jws
  • jws7-tomcat jboss enterprise web server 7.0 11.0.21-7.redhat_00006.1.el8jws
  • jws7-tomcat jboss enterprise web server 7.0 11.0.21-7.redhat_00006.1.el9jws
  • jws7-tomcat-lib jboss enterprise web server 7.0 11.0.21-7.redhat_00006.1.el10jws
  • jws7-tomcat-lib jboss enterprise web server 7.0 11.0.21-7.redhat_00006.1.el8jws
  • jws7-tomcat-lib jboss enterprise web server 7.0 11.0.21-7.redhat_00006.1.el9jws
  • jws7-tomcat-javadoc jboss enterprise web server 7.0 11.0.21-7.redhat_00006.1.el10jws
  • jws7-tomcat-javadoc jboss enterprise web server 7.0 11.0.21-7.redhat_00006.1.el8jws

red hat advisories RHSA-2026:76952RHSA-2026:73981RHSA-2026:56039

  • tomcat SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES for SAP 15 SP4 +8 more 9.0.121-150200.120.1
  • tomcat10 SLES for SAP 15 SP6, SLES for SAP 15 SP5, SLES 15 SP6-LTSS +4 more 10.1.59-150200.5.79.1
  • tomcat11 SLES for SAP 15 SP6, SLES 15 SP6-LTSS, SLE Module for Web and Scripting 15 SP7 11.0.25-150600.13.33.2
  • tomcat SLES 16.0, SLES for SAP applications 16.0 9.0.121-160000.1.1
  • tomcat11 SLES 16.0, SLES for SAP applications 16.0 11.0.25-160000.1.1
  • tomcat10 SLES 16.0, SLES for SAP applications 16.0 10.1.59-160000.1.1
  • tomcat SLES LTSS Extended Security 12 SP5, SLES 12 SP5-LTSS 9.0.121-3.177.3

suse advisories SUSE-SU-2026:4203-1SUSE-SU-2026:4126-1SUSE-SU-2026:4119-1SUSE-SU-2026:4114-1SUSE-SU-2026:23700-1SUSE-SU-2026:23720-1

  • tomcat openSUSE Tumbleweed 9.0.121-1.1
  • tomcat10 openSUSE Tumbleweed 10.1.59-1.1
  • tomcat11 openSUSE Tumbleweed 11.0.25-1.1
  • tomcat openSUSE Leap 16.0 9.0.121-160000.1.1
  • tomcat10 openSUSE Leap 16.0 10.1.59-160000.1.1
  • tomcat11 openSUSE Leap 16.0 11.0.25-160000.1.1

opensuse advisories openSUSE-SU-2026:11759-1openSUSE-SU-2026:11760-1openSUSE-SU-2026:11761-1openSUSE-SU-2026:21823-1openSUSE-SU-2026:21810-1openSUSE-SU-2026:21811-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-66299 updated cvss 5.3

tomcat: Apache Tomcat: Denial of Service via WebSocket chat example

  • Red Hat Enterprise Linux 8 tomcat, tomcat-lib, tomcat-webapps, tomcat-el-3.0-api, tomcat-docs-webapp, tomcat-jsp-2.3-api, +2 more Red Hat Enterprise Linux 9 tomcat, tomcat-lib, tomcat-webapps, tomcat-el-3.0-api, tomcat-docs-webapp, tomcat-jsp-2.3-api, +2 more Red Hat Enterprise Linux 10 tomcat, tomcat9
    affected: workaround, no fix available
  • Red Hat Hardened Images tomcat11 11.0.25-0.1.hum1, tomcat11-lib 11.0.25-0.1.hum1, tomcat11-common 11.0.25-0.1.hum1, tomcat11-webapps 11.0.25-0.1.hum1, tomcat11-el-6.0-api 11.0.25-0.1.hum1, tomcat11-docs-webapp 11.0.25-0.1.hum1, +4 more
    fixed: vendor fix RHSA-2026:56039
  • Red Hat JBoss Web Server 6.2 on RHEL 8 jws6-tomcat 10.1.49-16.redhat_00016.1.el8jws, jws6-tomcat-lib 10.1.49-16.redhat_00016.1.el8jws, jws6-tomcat-javadoc 10.1.49-16.redhat_00016.1.el8jws, jws6-tomcat-selinux 10.1.49-16.redhat_00016.1.el8jws, jws6-tomcat-webapps 10.1.49-16.redhat_00016.1.el8jws, jws6-tomcat-el-5.0-api 10.1.49-16.redhat_00016.1.el8jws, +4 more Red Hat JBoss Web Server 6.2 on RHEL 9 jws6-tomcat 10.1.49-16.redhat_00016.1.el9jws, jws6-tomcat-lib 10.1.49-16.redhat_00016.1.el9jws, jws6-tomcat-javadoc 10.1.49-16.redhat_00016.1.el9jws, jws6-tomcat-selinux 10.1.49-16.redhat_00016.1.el9jws, jws6-tomcat-webapps 10.1.49-16.redhat_00016.1.el9jws, jws6-tomcat-el-5.0-api 10.1.49-16.redhat_00016.1.el9jws, +4 more Red Hat JBoss Web Server 6.2 on RHEL 10 jws6-tomcat 10.1.49-16.redhat_00016.1.el10jws, jws6-tomcat-lib 10.1.49-16.redhat_00016.1.el10jws, jws6-tomcat-javadoc 10.1.49-16.redhat_00016.1.el10jws, jws6-tomcat-selinux 10.1.49-16.redhat_00016.1.el10jws, jws6-tomcat-webapps 10.1.49-16.redhat_00016.1.el10jws, jws6-tomcat-el-5.0-api 10.1.49-16.redhat_00016.1.el10jws, +4 more
    fixed: vendor fix RHSA-2026:73981
  • Red Hat JBoss Web Server 6.2.5
    fixed: vendor fix RHSA-2026:73982
  • Red Hat JBoss Web Server 7.0.2
    fixed: vendor fix RHSA-2026:76956
  • Red Hat Enterprise Linux 6 tomcat6, tomcat6-lib, tomcat6-log4j, tomcat6-javadoc, tomcat6-webapps, tomcat6-el-2.1-api, +4 more Red Hat Enterprise Linux 7 tomcat, tomcat-lib, tomcat-jsvc, tomcat-javadoc, tomcat-webapps, tomcat-el-2.2-api, +4 more Red Hat Enterprise Linux 8 pki-servlet-engine, pki-servlet-4.0-api Red Hat Enterprise Linux 9 pki-servlet-engine, pki-servlet-4.0-api Red Hat Hardened Images tomcat10 10.1.57-3.1.hum1 Red Hat JBoss Web Server 5 jws5-tomcat, jws5-tomcat-lib, jws5-tomcat-jsvc, jws5-tomcat-javadoc, jws5-tomcat-selinux, jws5-tomcat-webapps, +7 more
    +1 more products
    Red Hat JBoss Web Server 7 tomcat
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
yes
Technical impact
partial
Assessed
3 mo ago

Exploit prediction

0.55% chance of exploitation in the next 30 days, higher than 46% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CISA ADP 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 5.3 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
bitnami tomcat
<9.0.121
>=10.1.24, <10.1.58
>=11.0.0, <11.0.25
9.0.121
10.1.58
11.0.25

Affected products

  • Apache Software Foundation Apache Tomcat

Classification

Weakness
  • CWE-400 Uncontrolled Resource Consumption

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.