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CVE-2026-66299

HIGH 7.5

Published 2026-07-28 · Last modified 2026-07-28

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.

ELEVATED IMPACT

Severe if exploited (CVSS 7.5), but no known exploitation and low modeled probability. Patch on a normal cadence.

Exploitation likelihood

0.5%chance of exploitation in 30 days · 38th percentile

○ In CISA KEV ○ Public exploit / PoC

Impact if exploited

7.5CVSS 3.1 · HIGH

  • ConfidentialityNone
  • IntegrityNone
  • AvailabilityHigh

What an attacker needs

  • ✓Access: Reachable over the network — no local access needed
  • ✓Privileges: No account or privileges required
  • ✓User interaction: No user interaction needed
  • ✓Complexity: No special conditions — reliably repeatable

✓ lowers the bar for an attacker · ⚠ raises it

Proof of concept & exploit code

Test against your own equipment

curl -s https://vulnpedia.com/cve/CVE-2026-66299/poc.jsonMachine-readable PoC index for this CVE (for automation).

Listed for defensive triage, patch verification, and authorized testing on systems you own. Machine-readable: /cve/CVE-2026-66299/poc.json

Affected

Vendors Apache Software Foundation Apache

Products Apache Tomcat Tomcat

Weakness (CWE)

  • CWE-400: Uncontrolled Resource Consumption

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Known Affected Software Configurations

VendorProductVersion range
ApacheTomcat≥ 9.0.89 and < 9.0.121
ApacheTomcat≥ 10.1.24 and < 10.1.58
ApacheTomcat≥ 11.0.1 and < 11.0.25
ApacheTomcat11.0.0
ApacheTomcat11.0.0
ApacheTomcat11.0.0
ApacheTomcat11.0.0
ApacheTomcat11.0.0
ApacheTomcat11.0.0
ApacheTomcat11.0.0

All CVSS metrics

  • HIGH 7.5 v3.1 · ADP Primary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
  • HIGH 7.5 v3.1 · NVD Secondary
    CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

References

Advisories

Sources: NVD · CVE.org · EPSS