CVE Intelligence
High Denial of service

CVE-2020-13935 — Infinite Loop in Apache Software Foundation Tomcat

The payload length in a WebSocket frame was not correctly validated in Apache Tomcat 10.0.0-M1 to 10.0.0-M6, 9.0.0.M1 to 9.0.36, 8.5.0 to 8.5.56 and 7.0.27 to 7.0.104. Invalid payload lengths could trigger an infinite loop. Multiple requests with invalid payload lengths could lead 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 86.6% (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
86.61%
ahead of 100% of scored CVEs · Oct 14, 2026
Affects
Apache Software Foundation
Tomcat and 17 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)
  • 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 100% of scored CVEs: prioritize it in the patch queue.
  5. Search available logs for exploit probes matching the vulnerability class (denial of service), 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-milestone2version 9.0.0-milestone20version 9.0.0-milestone21version 9.0.0-milestone22version 9.0.0-milestone23version 9.0.0-milestone24
and 28 more version 9.0.0-milestone25version 9.0.0-milestone26version 9.0.0-milestone18version 9.0.0-milestone3version 9.0.0-milestone4version 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-milestone1version 10.0.0-milestone6version 10.0.0-milestone5version 10.0.0-milestone4version 10.0.0-milestone3≥ 7.0.27 and ≤ 7.0.104≥ 8.5.0 and ≤ 8.5.56≥ 9.0.1 and ≤ 9.0.36version 9.0.0-milestone10version 9.0.0-milestone11version 9.0.0-milestone12version 9.0.0-milestone13version 9.0.0-milestone14version 9.0.0-milestone15version 9.0.0-milestone16version 9.0.0-milestone17
Vulnerable NIST National Vulnerability Database
Canonical Ubuntu Linux version 20.04version 16.04 Vulnerable NIST National Vulnerability Database
Debian Debian Linux version 10.0version 9.0 Vulnerable NIST National Vulnerability Database
Mcafee Epolicy Orchestrator version 5.10.0-update_8version 5.9.0version 5.9.1version 5.10.0version 5.10.0-update_1version 5.10.0-update_2version 5.10.0-update_3version 5.10.0-update_4
and 3 more version 5.10.0-update_5version 5.10.0-update_6version 5.10.0-update_7
Vulnerable NIST National Vulnerability Database
Netapp Oncommand System Manager ≥ 3.0.0 and ≤ 3.1.3 Vulnerable NIST National Vulnerability Database
Opensuse Leap version 15.2version 15.1 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 9.3.6version 9.3.3 Vulnerable NIST National Vulnerability Database
Oracle Blockchain Platform < 21.1.2 Vulnerable NIST National Vulnerability Database
Oracle Commerce Guided Search version 11.3.2 Vulnerable NIST National Vulnerability Database
Oracle Communications Cloud Native Core Policy version 1.14.0 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 12.2.1.4.0version 12.2.1.3.0 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 19cversion 18c 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-835 · Infinite Loop

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 86.61%

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).
  • Track CPU/memory spikes and availability drops correlated with request patterns.
web/proxy/WAF logsnetwork IDS/IPSresource metrics

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

17 on the record

Elsewhere on this site

Apache Software Foundation
every CVE for this vendor
Denial of service
same class
CWE-835
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-2026-55957 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-2026-55956 Apache Tomcat: Security constraints for default servlet ignored method Jun 29, 2026
  • CVE-2026-53434 Apache Tomcat CRL Configuration Flaw in FFM Connector (CWE-390) 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-2020-13935 is "Infinite Loop 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 86.61% 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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