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Vulnerabilities

Vulnerability · CVE-2020-13934

An h2c direct connection to Apache Tomcat 10.0.0-M1 to 10.0.0-M6, 9.0.0.M5 to 9.0.36 and 8.5.1 to 8.5.56 did not release the HTTP/1.1 processor after the upgrade to HTTP/2.

Published Jul 14, 2020 · catalog updated Oct 8, 2026 · An h2c direct connection

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check this week

CVE-2020-13934 is not in CISA KEV. FIRST estimates a 64.12% chance of exploitation in the next 30 days. Check whether you run An h2c direct connection.

Gaps on this record

  • The stored product name is a package slug. The name on this page is taken from the title (An h2c direct connection).
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.

Same product and reporting

Severity
High7.5
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
64.12%
Remediation
Version ranges on file
Affected products
cpe apache/tomcat

An h2c direct connection to Apache Tomcat 10.0.0-M1 to 10.0.0-M6, 9.0.0.M5 to 9.0.36 and 8.5.1 to 8.5.56 did not release the HTTP/1.1 processor after the upgrade to HTTP/2. If a sufficient number of such requests were made, an OutOfMemoryException could occur leading to a denial of service.

Are you affected?

Enter the version you run. The result uses only the ranges stored on this record.

The check returns affected, not affected, or incomplete. It does not guess a version that is missing from the record.

  • cpe apache/tomcat9.0.0
  • cpe apache/tomcat>= 8.5.1, <= 8.5.56
  • cpe apache/tomcat>= 9.0.1, <= 9.0.36

How to fix CVE-2020-13934

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

CVE-2020-13934 is not in CISA KEV. FIRST estimates a 64.12% chance of exploitation in the next 30 days. Check whether you run An h2c direct connection.

Which versions are affected?

Compare what you have installed with 9.0.0, >= 8.5.1, <= 8.5.56, >= 9.0.1, <= 9.0.36. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-401: Missing Release of Memory after Effective Lifetime; CWE-476: NULL Pointer Dereference. EPSS 64.12%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Apache Tomcat security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Jul 14, 2020 · Monitored products — critical

    Detected

    An h2c direct connection to Apache Tomcat 10.0.0-M1 to 10.0.0-M6, 9.0.0.M5 to 9.0.36 and 8.5.1 to 8.5.56 did not release the HTTP/1.1 processor after the upgrade to HTTP/2. If a sufficient number of such requests were made, an OutOfMemoryException could occur leading to a denial of service.

  2. Oct 8, 2026 · Monitored products — critical

    Updated

    An h2c direct connection to Apache Tomcat 10.0.0-M1 to 10.0.0-M6, 9.0.0.M5 to 9.0.36 and 8.5.1 to 8.5.56 did not release the HTTP/1.1 processor after the upgrade to HTTP/2. If a sufficient number of such requests were made, an OutOfMemoryException could occur leading to a denial of service.

Sources

  • CVE.orgVulnerability recordCVE-2020-13934

    Official CVE identifier

    cve.org
  • Monitored products — criticalVendor advisoryCVE-2020-13934

    An h2c direct connection to Apache Tomcat 10.0.0-M1 to 10.0.0-M6, 9.0.0.M5 to 9.0.36 and 8.5.1 to 8.5.56 did not release the HTTP/1.1 processor after the upgrade to HTTP/2. If a sufficient number of such requests were made, an OutOfMemoryException could occur leading to a denial of service.

    nvd.nist.gov

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • CVE.orgNov 4, 2026
  • Monitored products — criticalNov 3, 2026