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VulnerabilityPublished

CVE-2026-78383: Apache Tomcat · Unthrottled Resource Allocation

Affects Apache TomcatSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High.

Data as of 6 Nov 2026, 23:24 UTC

CVSS 3.1 base score
7.5High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.5% chance of exploitation in 30 days – higher than 43% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 23 Sep 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 7 Nov 2026.

What to do

Affected software

ProductAffectedFixed in
Apache Software FoundationApache TomcatAffected
  • >=11.0.0-M1 <=11.0.25
  • >=10.1.0-M1 <=10.1.59
  • >=9.0.0.M1 <=9.0.121
  • >=8.5.0 <=8.5.100
  • >=7.0.0 <=7.0.109
Fixed in–
Mavenorg.apache.tomcat/tomcatpkg:maven/org.apache.tomcat/tomcatOther threatsAffected
  • >=11.0.0-M1 <=11.0.25
  • >=10.1.0-M1 <=10.1.59
  • >=9.0.0.M1 <=9.0.121
  • >=8.5.0 <=8.5.100
  • >=7.0.0 <=7.0.109
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

Users should upgrade affected Apache Tomcat versions to 11.0.26, 10.1.60, or 9.0.122 where the issue is fixed. No other mitigations or temporary workarounds are specified. Applying the official vendor fix is the recommended remediation.

Description

CVE-2026-78383 is a high severity vulnerability in Apache Tomcat involving allocation of resources without limits or throttling. It allows an unauthenticated AJP request to pin an AJP processing thread, causing denial of service. Affected versions include Apache Tomcat from 11.0.0-M1 through 11.0.25, 10.1.0-M1 through 10.1.59, 9.0.0.M1 through 9.0.121, and some older EOL versions. Upgrading to versions 11.0.26, 10.1.60, or 9.0.122 mitigates the issue.

References

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