CVE-2020-13943

MEDIUMNVD 4.34.3
EchelonGraph scoreLOW confidence

This medium-severity CVE scores 4.3 under NVD CVSS v3. EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: nvd
Elevated
4.3
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • 45 internet-exposed hosts are running an affected version right now
  • High exploitation likelihood — EPSS 57%
CISA-KEV: Not listedEPSS: 57%CVSS: 4.3Exploit: NoneExposed: 45

A fix is available — apply it.

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.

Live · internet exposure

45 internet-exposed hosts are running an affected version of CVE-2020-13943 right now.

across 19 countries (Germany, United States, China, Singapore, France)top: tomcat
See the live KEV-Exposure radar →Found passively from public internet-scan data — aggregate, host-redacted.

EchelonGraph is the only CVE feed that fuses live vulnerability intelligence with its own live internet-exposure radar — so you see not just that a CVE is exploited, but how much of the internet is exposed to it right now.

CVSS v3
4.3
EG Score
4.3(low)
EPSS
99.0%
KEV
Not listed

Published

October 12, 2020

Last Modified

November 21, 2024

References (14)

Vendor Advisories for CVE-2020-13943(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(3)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntutomcat9-examples (9.0.31-1ubuntu0.2) @ focal2026-05-23ubuntu
redhattomcat2021-12-14redhat
redhatjws5-tomcat-native-0:1.2.25-3.redhat_3.el8jws2021-02-11redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
org.apache.tomcat:tomcat-coyote8.5.0 ... 8.5.9 (46 versions)8.5.58—

Additional Vendor Advisories

(4)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 4× in last 7d / 33× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-11 08:24 UTCEPSS rescore
  2. 2026-07-09 19:06 UTCEPSS rescore
  3. 2026-07-07 13:43 UTCEPSS rescore
  4. 2026-07-05 02:27 UTCEPSS rescore
  5. 2026-07-01 15:03 UTCEPSS rescore
  6. 2026-07-01 15:03 UTCEPSS rescore
  7. 2026-06-30 23:20 UTCEPSS rescore
  8. 2026-06-30 23:20 UTCEPSS rescore
  9. 2026-06-28 14:05 UTCEPSS rescore
  10. 2026-06-28 04:54 UTCEPSS rescore
  11. 2026-06-28 04:54 UTCEPSS rescore
  12. 2026-06-27 03:06 UTCEPSS rescore
  13. 2026-06-25 13:47 UTCEPSS rescore
  14. 2026-06-25 13:47 UTCEPSS rescore
  15. 2026-06-24 10:50 UTCOSV refresh
  16. 2026-06-23 21:31 UTCEPSS rescore
  17. 2026-06-23 21:31 UTCEPSS rescore
  18. 2026-06-21 01:57 UTCEPSS rescore
  19. 2026-06-21 01:57 UTCEPSS rescore
  20. 2026-06-19 19:23 UTCEPSS rescore
  21. 2026-06-19 19:23 UTCEPSS rescore
  22. 2026-06-18 17:50 UTCEPSS rescore
  23. 2026-06-18 17:50 UTCEPSS rescore
  24. 2026-06-17 17:50 UTCEPSS rescore
  25. 2026-06-17 17:50 UTCEPSS rescore
Show 38 more
  1. 2026-06-16 17:50 UTCEPSS rescore
  2. 2026-06-16 17:50 UTCEPSS rescore
  3. 2026-06-15 17:46 UTCEPSS rescore
  4. 2026-06-14 23:15 UTCEPSS rescore
  5. 2026-06-14 23:15 UTCEPSS rescore
  6. 2026-06-13 22:58 UTCEPSS rescore
  7. 2026-06-13 22:58 UTCEPSS rescore
  8. 2026-06-12 23:09 UTCEPSS rescore
  9. 2026-06-11 13:58 UTCEPSS rescore
  10. 2026-06-10 22:16 UTCEPSS rescore
  11. 2026-06-10 22:16 UTCEPSS rescore
  12. 2026-06-10 13:20 UTCEPSS rescore
  13. 2026-06-08 14:15 UTCEPSS rescore
  14. 2026-06-08 14:15 UTCEPSS rescore
  15. 2026-06-07 15:23 UTCEPSS rescore
  16. 2026-06-07 15:23 UTCEPSS rescore
  17. 2026-06-07 15:21 UTCOSV refresh
  18. 2026-06-06 13:45 UTCEPSS rescore
  19. 2026-06-06 13:45 UTCEPSS rescore
  20. 2026-06-06 13:45 UTCEPSS rescore
  21. 2026-06-05 22:45 UTCEPSS rescore
  22. 2026-06-05 22:45 UTCEPSS rescore
  23. 2026-06-04 13:10 UTCEPSS rescore
  24. 2026-06-04 13:10 UTCEPSS rescore
  25. 2026-06-02 20:11 UTCEPSS rescore
  26. 2026-06-02 20:11 UTCEPSS rescore
  27. 2026-06-01 13:50 UTCEPSS rescore
  28. 2026-05-31 22:29 UTCEPSS rescore
  29. 2026-05-31 22:29 UTCEPSS rescore
  30. 2026-05-31 00:15 UTCEPSS rescore
  31. 2026-05-31 00:14 UTCEPSS rescore
  32. 2026-05-29 13:42 UTCEPSS rescore
  33. 2026-05-29 13:42 UTCEPSS rescore
  34. 2026-05-28 13:43 UTCEPSS rescore
  35. 2026-05-28 13:43 UTCEPSS rescore
  36. 2026-05-27 13:39 UTCEPSS rescore
  37. 2026-05-23 06:49 UTCEG score recompute
  38. 2026-05-23 06:49 UTCVendor advisory

Frequently asked(5)

What is CVE-2020-13943?
CVE-2020-13943 is a medium vulnerability published on October 12, 2020. 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…
When was CVE-2020-13943 disclosed?
CVE-2020-13943 was first published in the National Vulnerability Database on October 12, 2020, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2020-13943 actively exploited?
CVE-2020-13943 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 99.0% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2020-13943?
CVE-2020-13943 has a CVSS v3 base score of 4.3 (NVD). The EG score is currently aggregating — additional source signals are being incorporated as they become available..
How do I remediate CVE-2020-13943?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2020-13943, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

See which npm, PyPI, Go, and Maven packages are affected by CVE-2020-13943

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