CVE Intelligence
High Memory corruption

CVE-2020-13934 — Missing Release of Memory after Effective Lifetime in Apache Software Foundation 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.

Published Jul 14, 2020 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: apache

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.
How the score was calculated
  • EPSS 64.1% (30-day exploitation probability)+15
  • Technical severity (high)+6
  • Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation
Not confirmed
Not in CISA KEV — an absence of record, not proof it is unexploited.
EPSS FIRST
64.12%
ahead of 99% of scored CVEs · Oct 14, 2026
Affects
Apache Software Foundation
Tomcat and 13 more
CVSS base
7.5
High · 1 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation
None
none · proof-of-concept · active
Automatable
Yes
can an attacker script the kill-chain steps
Technical impact
Partial
partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)
  • Documented patch — www.oracle.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

  1. Identify exposed assets running the affected vendor/product/version combinations (Apache Software Foundation Tomcat, Canonical Ubuntu Linux, Debian Debian Linux…).
  2. The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
  3. Apply the fixed version or the patch documented under Remediation.
  4. EPSS ahead of 99% of scored CVEs: prioritize it in the patch queue.
  5. Search available logs for exploit probes matching the vulnerability class (memory corruption), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

VendorProductVersionsStatusSource
Apache Software Foundation Tomcat version 9.0.0-milestone27version 9.0.0-milestone19version 9.0.0-milestone20version 9.0.0-milestone21version 9.0.0-milestone22version 9.0.0-milestone23version 9.0.0-milestone24version 9.0.0-milestone25
and 23 more version 9.0.0-milestone26version 9.0.0-milestone18version 9.0.0-milestone5version 9.0.0-milestone6version 9.0.0-milestone7version 9.0.0-milestone8version 9.0.0-milestone9version 10.0.0-milestone1version 10.0.0-milestone2version 9.0.0-milestone17version 9.0.0-milestone16version 9.0.0-milestone15version 9.0.0-milestone14version 9.0.0-milestone13version 9.0.0-milestone12version 9.0.0-milestone11version 9.0.0-milestone10≥ 9.0.1 and ≤ 9.0.36≥ 8.5.1 and ≤ 8.5.56version 10.0.0-milestone3version 10.0.0-milestone4version 10.0.0-milestone5version 10.0.0-milestone6
Vulnerable NIST National Vulnerability Database
Canonical Ubuntu Linux version 20.04 Vulnerable NIST National Vulnerability Database
Debian Debian Linux version 10.0version 9.0 Vulnerable NIST National Vulnerability Database
Netapp Oncommand System Manager ≥ 3.0.0 and ≤ 3.1.3 Vulnerable NIST National Vulnerability Database
Opensuse Leap version 15.1version 15.2 Vulnerable NIST National Vulnerability Database
Oracle Agile Engineering Data Management version 6.2.1.0 Vulnerable NIST National Vulnerability Database
Oracle Agile Product Lifecycle Management version 9.3.5version 9.3.3version 9.3.6 Vulnerable NIST National Vulnerability Database
Oracle Communications Instant Messaging Server version 10.0.1.5.0 Vulnerable NIST National Vulnerability Database
Oracle Fmw Platform version 12.2.1.4.0version 12.2.1.3.0 Vulnerable NIST National Vulnerability Database
Oracle Instantis Enterprisetrack version 17.1version 17.2version 17.3 Vulnerable NIST National Vulnerability Database
Oracle Managed File Transfer version 12.2.1.3.0version 12.2.1.4.0 Vulnerable NIST National Vulnerability Database
Oracle Mysql Enterprise Monitor ≤ 8.0.21 Vulnerable NIST National Vulnerability Database
Oracle Siebel Ui Framework ≤ 20.12 Vulnerable NIST National Vulnerability Database
Oracle Workload Manager version 12.2.0.1version 18cversion 19c Vulnerable NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

ScoreVersionSeverityExpl.ImpactScored by
7.5 CVSS 3.1 High 3.9 3.6 nvd@nist.gov via NIST National Vulnerability Database
5.0 CVSS 2.0 Medium 10.0 2.9 nvd@nist.gov via NIST National Vulnerability Database
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-401 · Missing Release of Memory after Effective Lifetime

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 64.12%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

  • Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
  • Correlate service crashes/restarts with inbound traffic; repeated crashes may indicate attempts.
web/proxy/WAF logsnetwork IDS/IPSendpoint telemetry (EDR)crash dumps

Timeline

What happened to this CVE, newest first.

  • 2026
  • SSVC assessment updated
    Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
  • Record published
    Oct 13, 2026
  • Fix documented
    Oct 13, 2026 · NIST National Vulnerability Database
  • CVSS changed · 7.5
    Oct 13, 2026 · NIST National Vulnerability Database
  • Source status changed · → Modified
    Oct 13, 2026 · NIST National Vulnerability Database
  • Record created in this database
    Oct 13, 2026 · NIST National Vulnerability Database
  • 2020
  • CVE published
    Jul 14, 2020 · apache

Source activity

Repeated readings are counted rather than listed.

  • 1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

13 on the record

Elsewhere on this site

Apache Software Foundation
every CVE for this vendor
Memory corruption
same class
CWE-401
other pages naming this weakness

Related CVEs (same products)

  • CVE-2026-12996 A use-after-free in OpenVPN 2.6.0 through 2.6.20 and 2.7_alpha1 through 2.7.4 allows remote... Jul 30, 2026
  • CVE-2026-55956 Apache Tomcat: Security constraints for default servlet ignored method Jun 29, 2026
  • CVE-2026-55957 Apache Tomcat: Authentication bypass with JNDIRealm and GSSAPI authenticated bind Jun 29, 2026
  • CVE-2026-55276 Apache Tomcat: Logged effective web.xml is incomplete Jun 29, 2026
  • CVE-2026-55955 Apache Tomcat: EncryptInterceptor not protected against replay attacks Jun 29, 2026
  • CVE-2026-50229 Apache Tomcat: XSS in number guess example Jun 29, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

  • No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
  • No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
  • No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2020-13934 is "Missing Release of Memory after Effective Lifetime in Apache Software Foundation Tomcat", rated High. It affects Tomcat (Apache Software Foundation); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 7.5 describes technical severity. EPSS 64.12% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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