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CVE-2020-13943 Apache Tomcat

Affected softwareApache Tomcat
Severity4.3 Medium CVSS 3.1 2 scores
Fixed in10.0.0-M8, 9.0.38, 8.5.58
WeaknessInformation exposure (CWE-200)
Published12 Oct 2020
Updated8 Oct 2026

Description

If an HTTP/2 client connecting to Apache Tomcat 10.0.0-M1 to 10.0.0-M7, 9.0.0.M1 to 9.0.37 or 8.5.0 to 8.5.57 exceeded the agreed maximum number of concurrent streams for a connection (in violation of the HTTP/2 protocol), it was possible that a subsequent request made on that connection could contain HTTP headers - including HTTP/2 pseudo headers - from a previous request rather than the intended headers. This could lead to users seeing responses for unexpected resources.

Exploitation status

Forecast only (53% 30-day chance)

No exploit has been reported in the sources we check. EPSS puts this CVE in the top 1.0% of all scored CVEs. That is a model's forecast, not a report of exploitation.

  • CISA KEV not listed
  • VulnCheck KEV not listed
  • CISA Vulnrichment exploitation: none
  • Indexed PoC none indexed
  • EPSS 53% chance in 30 days A model's forecast, not a report of exploitation. Higher than 99% of all scored CVEs.

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.

A public code fix exists: apache/tomcat 1bbc650.

  • Protection none
  • Action unverified
  • Review automated Upstream data
  • Record active
Decided by 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
Finding This CVE is not listed in CISA KEV or VulnCheck KEV, CISA Vulnrichment records no active exploitation, no reviewed exploit catalogue carries an entry for it, and no GitHub PoC repository for it has 5 or more stars. Nobody has published exploit code worth tracing, so it is not a candidate for a rule ahead of the ones where somebody has; an upstream fix path does exist, so the remediation half of the candidacy still holds. This is a statement about what has been published, not about whether the defect is reachable or serious.

CVSS

4.3 MEDIUM v3.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N 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 4.3 MEDIUM CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N NVD Primary published
CVSS 2.0 4.0 none AV:N/AC:L/Au:S/C:P/I:N/A:N 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-coyote 10.0.0-M1 10.0.0-M8 unbounded
org.apache.tomcat:tomcat-coyote 9.0.0-M1 9.0.38 unbounded
org.apache.tomcat:tomcat-coyote 8.5.0 8.5.58 unbounded

Products and versions

5 products, 134 version entries
SourceVendorProductSchemeAffected versions
nvd apache tomcat generic 8.5.0 · 8.5.1 · 8.5.2 · 8.5.3 · 8.5.4 · 8.5.5 · 8.5.6 · 8.5.7 · 8.5.8 · 8.5.9 · 8.5.10 · 8.5.11 · 8.5.12 · 8.5.13 · 8.5.14 · 8.5.15 · 8.5.16 · 8.5.17 · 8.5.18 · 8.5.19 · 8.5.20 · 8.5.21 · 8.5.22 · 8.5.23 · 8.5.24 · 8.5.25 · 8.5.26 · 8.5.27 · 8.5.28 · 8.5.29 · 8.5.30 · 8.5.31 · 8.5.32 · 8.5.33 · 8.5.34 · 8.5.35 · 8.5.36 · 8.5.37 · 8.5.38 · 8.5.39 · 8.5.40 · 8.5.41 · 8.5.42 · 8.5.43 · 8.5.44 · 8.5.45 · 8.5.46 · 8.5.47 · 8.5.48 · 8.5.49 · 8.5.50 · 8.5.51 · 8.5.52 · 8.5.53 · 8.5.54 · 8.5.55 · 8.5.56 · 8.5.57 · 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: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:milestone5 · 9.0.0:milestone6 · 9.0.0:milestone7 · 9.0.0:milestone8 · 9.0.0:milestone9 · 9.0.1 · 9.0.2 · 9.0.3 · 9.0.4 · 9.0.5 · 9.0.6 · 9.0.7 · 9.0.8 · 9.0.9 · 9.0.10 · 9.0.11 · 9.0.12 · 9.0.13 · 9.0.14 · 9.0.15 · 9.0.16 · 9.0.17 · 9.0.18 · 9.0.19 · 9.0.20 · 9.0.21 · 9.0.22 · 9.0.23 · 9.0.24 · 9.0.25 · 9.0.26 · 9.0.27 · 9.0.28 · 9.0.29 · 9.0.30 · 9.0.31 · 9.0.32 · 9.0.33 · 9.0.34 · 9.0.35 · 9.0.36 · 9.0.37 · 10.0.0:milestone1 · 10.0.0:milestone2 · 10.0.0:milestone3 · 10.0.0:milestone4 · 10.0.0:milestone5 · 10.0.0:milestone6 · 10.0.0:milestone7
nvd debian debian linux generic 9.0 · 10.0
nvd oracle instantis enterprisetrack generic 17.1 · 17.2 · 17.3
nvd oracle sd-wan edge generic 9.0
osv org.apache.tomcat tomcat-coyote generic ≥ 8.5.0 and < 8.5.58 · ≥ 9.0.0 and < 9.0.38 · ≥ 10.0.0 and < 10.0.0

References

URLTags
https://github.com/apache/tomcat/commit/1bbc650cbc3f08d85a1ec6d803c47ae53a84f3bb WEB
https://github.com/apache/tomcat/commit/55911430df13f8c9998fbdee1f9716994d2db59b WEB
https://github.com/apache/tomcat/commit/9d7def063b47407a09a2f9202beed99f4dcb292a WEB
https://lists.apache.org/thread.html/r4a390027eb27e4550142fac6c8317cc684b157ae314d31514747f307%40%3Cannounce.tomcat.apache.org%3E WEB
https://lists.debian.org/debian-lts-announce/2020/10/msg00019.html WEB
https://security.netapp.com/advisory/ntap-20201016-0007 WEB
https://www.debian.org/security/2021/dsa-4835 WEB
https://www.oracle.com/security-alerts/cpuApr2021.html WEB
http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00002.html WEB
http://lists.opensuse.org/opensuse-security-announce/2020-11/msg00021.html WEB

Timeline

Published2020-10-12By the CVE Program.
NVD record modified2026-10-08NVD's own last-modified date for this record.