`CVE-2026-66299` Apache Tomcat

Affected software	Apache Tomcat
Severity	7.5 High CVSS 3.1 2 scores
Weakness	Uncontrolled resource consumption (CWE-400)
Published	28 Jul 2026
Updated	24 Oct 2026

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.

Exploitation status

No public exploit

No exploit has been reported in the sources we check.

CISA KEV not listed
VulnCheck KEV not listed
CISA Vulnrichment exploitation: none
Indexed PoC none indexed
EPSS 0.55% chance in 30 days

Waratek protection

No exploit published

Within Waratek scope. In the sources we check, nobody has published exploit code for this CVE or reported it being exploited.

VRT has not found a public code change for this CVE yet.

Protection none
Action not pursued
Review automated Upstream data
Record active

Decided by	Nothing to build a rule from yet: no published exploit, no CISA record of exploitation and no source-level change to read
Finding	This CVE affects a known product, but nothing published names a fix and nothing published shows an exploit. That is a statement about the evidence, not about the defect — it does not mean the vulnerability is unimportant or unreachable, only that neither of the two things VRT can act on exists.

Decided by

Nothing to build a rule from yet: no published exploit, no CISA record of exploitation and no source-level change to read

Finding

This CVE affects a known product, but nothing published names a fix and nothing published shows an exploit. That is a statement about the evidence, not about the defect — it does not mean the vulnerability is unimportant or unreachable, only that neither of the two things VRT can act on exists.

CVSS

7.5 HIGH v3.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H 2 metrics

We show the highest score from the newest CVSS version. Scores from different versions can't be compared, and the first score listed is sometimes a 0.0 placeholder.

Version Score Band Vector Assigner Type

CVSS 3.1 7.5 HIGH CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H CISA-ADP Secondary published

CVSS 3.1 5.3 MEDIUM CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L NVD Primary

Version	Score	Band	Vector	Assigner	Type
CVSS 3.1	7.5	HIGH	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`	CISA-ADP	Secondary	published
CVSS 3.1	5.3	MEDIUM	`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L`	NVD	Primary

Affected software and releases

Oracle advisories

Advisory	Type	Quarter	Products Oracle names in its risk matrix
Oracle Critical Patch Update October 2026 ↗	CPU	2026-Q4	Oracle Supply Chain / Folders & Files Attachment (Apache Tomcat) (9.3.6)
Oracle Critical Security Patch Update September 2026 ↗	CSPU	2026-Q3	Oracle Communications / Core (Apache Tomcat) (6.1.1-7.0.0)

Advisory

Type

Quarter

Products Oracle names in its risk matrix

Oracle Critical Patch Update October 2026 ↗

CPU

2026-Q4

Oracle Supply Chain / Folders & Files Attachment (Apache Tomcat) (9.3.6)

Oracle Critical Security Patch Update September 2026 ↗

CSPU

2026-Q3

Oracle Communications / Core (Apache Tomcat) (6.1.1-7.0.0)

Oracle components and versions

Family	Component	Versions, as Oracle lists them	Read as
Oracle Communications	Core (Apache Tomcat)	6.1.1-7.0.0
Oracle Supply Chain	Folders & Files Attachment (Apache Tomcat)	9.3.6	9.3.6

Products and versions

1 product, 10 version entries

Source	Vendor	Product	Scheme	Affected versions
nvd	apache	tomcat	generic	≥ 9.0.89 and ＜ 9.0.121 · ≥ 10.1.24 and ＜ 10.1.58 · 11.0.0:milestone20 · 11.0.0:milestone21 · 11.0.0:milestone22 · 11.0.0:milestone23 · 11.0.0:milestone24 · 11.0.0:milestone25 · 11.0.0:milestone26 · ≥ 11.0.1 and ＜ 11.0.25

Source

Vendor

Product

Scheme

Affected versions

nvd

apache

tomcat

generic

≥ 9.0.89 and ＜ 9.0.121 · ≥ 10.1.24 and ＜ 10.1.58 · 11.0.0:milestone20 · 11.0.0:milestone21 · 11.0.0:milestone22 · 11.0.0:milestone23 · 11.0.0:milestone24 · 11.0.0:milestone25 · 11.0.0:milestone26 · ≥ 11.0.1 and ＜ 11.0.25

References

URL	Tags
https://lists.apache.org/thread/8owczcc1o8qw1rxmg9gvfk4w2jnh4l5k	Mailing List, Vendor Advisory
http://www.openwall.com/lists/oss-security/2026/07/28/25	Mailing List, Third Party Advisory

URL

Timeline

Published	2026-07-28	By the CVE Program.
NVD record modified	2026-10-24	NVD's own last-modified date for this record.

Published

2026-07-28

By the CVE Program.

NVD record modified

2026-10-24

NVD's own last-modified date for this record.

How VRT decided (19 of 24 rules ran)

19 of 24 rules ran. The rest didn't run because an earlier rule had already settled the CVE.

# Rule Outcome Status Detail

identity: Does this identifier describe a vulnerability at all? the first rule that matches decides

1 rejected no match CVE Program withdrawal of this identifier

scope: Is it a vulnerability Waratek protects? the first rule that matches decides

2 armr-patch-file no match An ARMR patch file on disk for this CVE

3 armr-secure-rule-file no match An ARMR security-rule template on disk for this CVE

4 manual-classification no match A researcher's recorded decision for this specific CVE

5 manual classification no match Manual classification of this CVE in the legacy dataset

6 non-java-upstream no match A root cause in non-Java code: an OS kernel, a C library, or a bundled runtime

7 oracle-component no match The defect being in a component of a tracked product the agent does not reach: JavaFX, the Java SE installer, the JInitiator browser plug-in, the native WebLogic proxy plug-in, or a native part of Oracle Application Server or Collaboration Suite (HTTP Server, Web Cache, Internet Directory, mail and calendar servers). Oracle gives these no CPE of their own and names them only in the description.

8 java-client-side no match Oracle's own risk-matrix note saying the CVE is reached only through untrusted code in the Java sandbox (applets, Web Start) or only through a client installation of Java, so a server running its own trusted code is not exposed

9 osv-maven no match An OSV.dev record of this CVE affecting a package published to Maven Central. When every such package is one business applications do not use (Minecraft mods and launchers, Fastjson) and no tracked product is named by CPE, it settles the CVE as Outside Waratek scope instead

10 cna-maven-package no match An affected Maven artifact named by the CNA itself

11 known-cpe-product matched In scope Matches known products: apache/tomcat

12 cna-cpe-product not reached A CPE the CNA published naming a tracked product. Oracle publishes these on advisory day, months before NVD.

13 oracle-advisory-family not reached A tracked product family named in Oracle's own risk matrix. CPE cannot carry a suite name, only a module.

14 cna-named-product not reached A tracked product named in words by the CVE's own CNA, on a record with no CPE yet. Apache and Eclipse publish these on advisory day, before NVD adds CPE data.

15 non-deployable-product not reached The only affected product being a sealed appliance image, where Java runs but no -javaagent can be attached

16 unmatched-product not reached No tracked product matched above, and none present at all

disposition: What do we do about one that is? every rule runs

17 patch-hint no match A reference pointing at the upstream fix: a commit, a PR, a Red Hat bug

18 open-source-maven no match The affected package being open source on Maven, so the fix can be read

19 poc-derivable no match An indexed exploit clearing the evidence bar to reverse-engineer, where there is no source to read

20 no-exploit decided it matched No exploit published No public exploits or POCs found in Exploit-DB, Nuclei templates, Metasploit modules, or GitHub POC repositories, and CISA's Vulnrichment assessment records no demonstrated exploit. No upstream fix reference or open-source Maven package was found either, so there is nothing to act on from either direction.

21 secure-rule-match no match A vulnerability class already blocked by an ARMR security rule

22 exploited-no-fix-or-poc skipped Somebody exploiting this CVE (a CISA or VulnCheck KEV listing, or a CISA verdict of active exploitation), with no fix, source code or PoC to build a rule from

23 below-action-threshold skipped Medium or Low severity, no CISA or VulnCheck KEV listing, no PoC clearing the evidence bar, no CISA verdict, no Oracle advisory

24 no-exploit-published skipped Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all

Products the scope rules checked

The products this CVE's record names, and whether VRT tracks each one. The scope rules decided on these.

Vendor Product Tracked CPE Source

apache tomcat tracked cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:* yaml

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