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CVE-2020-11996 Apache Tomcat

Affected softwareApache Tomcat
Severity7.5 High CVSS 3.1 2 scores
Fixed in10.0.0-M5, 9.0.35, 8.5.55
WeaknessUncontrolled resource consumption (CWE-400)
Published26 Jun 2020
Updated8 Oct 2026

Description

A specially crafted sequence of HTTP/2 requests sent to Apache Tomcat 10.0.0-M1 to 10.0.0-M5, 9.0.0.M1 to 9.0.35 and 8.5.0 to 8.5.55 could trigger high CPU usage for several seconds. If a sufficient number of such requests were made on concurrent HTTP/2 connections, the server could become unresponsive.

Exploitation status

Proof of concept only

A proof of concept exists, but no reviewed exploit catalogue lists this CVE.

  • CISA KEV not listed
  • VulnCheck KEV not listed
  • CISA Vulnrichment exploitation: none
  • Indexed PoC 1 indexed Published artifacts you can open, in GitHub PoC; first seen 2020-07-27.
  • EPSS 27% chance in 30 days A model's forecast, not a report of exploitation. Higher than 98% of all scored CVEs.
IndexArtifactStarsFirst seen
GitHub PoC tomcat-embed-core-9.0.31 CVE-2020-11996 Test PoC 5 2020-07-27

Waratek protection

Mitigation candidate

A kind of vulnerability Waratek's rules address, with exploit code published or exploitation reported. No rule exists and none is planned yet. The decision below says what we found to build a rule from.

  • Protection none
  • Action unverified
  • Review automated Inferred
  • Record active
Decided by The affected package being open source on Maven, so the fix can be read
Finding This CVE affects an open-source Java library published on Maven Central (Maven packages: org.apache.tomcat:tomcat, org.apache.tomcat.embed:tomcat-embed-core), so it is squarely in ARMR's territory and the source needed to understand the defect is public. That makes it a candidate for an ARMR patch rule. No rule exists and none is scheduled: the diff between the affected and fixed versions has not been read, and a closer look may find no hook point ARMR can act on.

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.

VersionScoreBandVectorAssignerType
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 NVD Primary published
CVSS 2.0 5.0 none AV:N/AC:L/Au:N/C:N/I:N/A:P NVD Primary

Affected software and releases

Oracle advisories

AdvisoryTypeQuarterProducts Oracle names in its risk matrix
Oracle Critical Patch Update April 2025 ↗ CPU 2025-Q2 Oracle Autonomous Health Framework / Trace File Analyzer (Apache Tomcat) (23.8.0-23.11.0, 24.1.0-24.11.0, 25.1.0, 25.2.0)

Oracle components and versions

FamilyComponentVersions, as Oracle lists themRead as
Oracle Autonomous Health Framework Trace File Analyzer (Apache Tomcat) 23.8.0-23.11.0, 24.1.0-24.11.0, 25.1.0, 25.2.0 25.1.0 · 25.2.0

Maven packages

Affected and fixed versions, from OSV.dev
PackageIntroducedFixedLast affected
org.apache.tomcat:tomcat 10.0.0-M1 10.0.0-M5 unbounded
org.apache.tomcat:tomcat 9.0.0.M1 9.0.35 unbounded
org.apache.tomcat:tomcat 8.5.0 8.5.55 unbounded
org.apache.tomcat.embed:tomcat-embed-core 10.0.0-M1 10.0.0-M5 unbounded
org.apache.tomcat.embed:tomcat-embed-core 9.0.0.M1 9.0.35 unbounded
org.apache.tomcat.embed:tomcat-embed-core 8.5.0 8.5.55 unbounded

Products and versions

10 products, 52 version entries
SourceVendorProductSchemeAffected versions
nvd apache tomcat generic ≥ 8.5.0 and ≤ 8.5.55 · 9.0.0:milestone1 · 9.0.0:milestone10 · 9.0.0:milestone11 · 9.0.0:milestone12 · 9.0.0:milestone13 · 9.0.0:milestone14 · 9.0.0:milestone15 · 9.0.0:milestone16 · 9.0.0:milestone17 · 9.0.0:milestone18 · 9.0.0:milestone19 · 9.0.0:milestone2 · 9.0.0:milestone20 · 9.0.0:milestone21 · 9.0.0:milestone22 · 9.0.0:milestone23 · 9.0.0:milestone24 · 9.0.0:milestone25 · 9.0.0:milestone26 · 9.0.0:milestone27 · 9.0.0:milestone3 · 9.0.0:milestone4 · 9.0.0:milestone5 · 9.0.0:milestone6 · 9.0.0:milestone7 · 9.0.0:milestone8 · 9.0.0:milestone9 · ≥ 9.0.0 and ≤ 9.0.35 · 10.0.0:milestone1 · 10.0.0:milestone2 · 10.0.0:milestone3 · 10.0.0:milestone4 · 10.0.0:milestone5
nvd canonical ubuntu linux generic 20.04
nvd debian debian linux generic 9.0 · 10.0
nvd netapp oncommand system manager generic 3.0 · 3.1.3
nvd opensuse leap generic 15.1 · 15.2
nvd oracle mysql enterprise monitor generic ≤ 8.0.21
nvd oracle siebel ui framework generic ≤ 20.12
nvd oracle workload manager generic 12.2.0.1 · 18c · 19c
osv org.apache.tomcat tomcat generic ≥ 8.5.0 and < 8.5.55 · ≥ 9.0.0 and < 9.0.35 · ≥ 10.0.0 and < 10.0.0
osv org.apache.tomcat.embed tomcat-embed-core generic ≥ 8.5.0 and < 8.5.55 · ≥ 9.0.0 and < 9.0.35 · ≥ 10.0.0 and < 10.0.0

References

URLTags
https://github.com/apache/tomcat/commit/9434a44d3449d620b1be70206819f8275b4a7509 WEB
https://github.com/apache/tomcat/commit/9a0231683a77e2957cea0fdee88b193b30b0c976 WEB
https://github.com/apache/tomcat/commit/c8acd2ab7371e39aeca7c306f3b5380f00afe552 WEB
https://lists.apache.org/thread.html/rb820f1a2a02bf07414be12c653c2ab5321fd87b9bf6c5e635c53ff4b@%3Cnotifications.ofbiz.apache.org%3E WEB
https://lists.apache.org/thread.html/rc80b96b4b96618b2b7461cb90664a428cfd6605eea9f74e51b792542@%3Cnotifications.ofbiz.apache.org%3E WEB
https://lists.apache.org/thread.html/rea65d6ef2e45dd1c45faae83922042732866c7b88fa109b76c83db52@%3Cnotifications.ofbiz.apache.org%3E WEB
https://lists.apache.org/thread.html/ref0339792ac6dac1dba83c071a727ad72380899bde60f6aaad4031b9@%3Cnotifications.ofbiz.apache.org%3E WEB
https://lists.debian.org/debian-lts-announce/2020/07/msg00010.html WEB
https://security.netapp.com/advisory/ntap-20200709-0002 WEB
https://tomcat.apache.org/security-10.html WEB

Timeline

Published2020-06-26By the CVE Program.
NVD record modified2026-10-08NVD's own last-modified date for this record.