CVE-2020-13935

CVE-2020-13935 is a high-severity vulnerability in Apache Tomcat with a CVSS 3.x base score of 7.5. Its EPSS exploit-prediction score of 88% places it in the 100th percentile, indicating an elevated likelihood of exploitation. The underlying weakness is classified as CWE-835.

Key facts

• Severity: High (CVSS 3.x base score 7.5)
• CVSS v2: 5.0
• EPSS exploit prediction: 88% (100th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-835
• Affected product: Apache Tomcat
• Published: 2020-07-14
• Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2020-13935?

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.

How severe is CVE-2020-13935?

CVE-2020-13935 has a CVSS 3.x base score of 7.5, rated high severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2020-13935 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 88% (100th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2020-13935?

CVE-2020-13935 primarily affects Apache Tomcat. In total, 72 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2020-13935?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its high severity, prioritise patching exposed systems.

When was CVE-2020-13935 published?

CVE-2020-13935 was published on 2020-07-14 and last updated on 2026-06-17.

References

• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00084.html
• http://lists.opensuse.org/opensuse-security-announce/2020-07/msg00088.html
• https://kc.mcafee.com/corporate/index?page=content&id=SB10332
• https://lists.apache.org/thread.html/r4e5d3c09f4dd2923191e972408b40fb8b42dbff0bc7904d44b651e50%40%3Cusers.tomcat.apache.org%3E
• https://lists.apache.org/thread.html/rd48c72bd3255bda87564d4da3791517c074d94f8a701f93b85752651%40%3Cannounce.tomcat.apache.org%3E
• https://lists.debian.org/debian-lts-announce/2020/07/msg00017.html
• https://security.netapp.com/advisory/ntap-20200724-0003/
• https://usn.ubuntu.com/4448-1/
• https://usn.ubuntu.com/4596-1/
• https://www.debian.org/security/2020/dsa-4727
• https://www.oracle.com//security-alerts/cpujul2021.html
• https://www.oracle.com/security-alerts/cpuApr2021.html
• https://www.oracle.com/security-alerts/cpuapr2022.html
• https://www.oracle.com/security-alerts/cpujan2021.html
• https://www.oracle.com/security-alerts/cpujan2022.html
• https://www.oracle.com/security-alerts/cpuoct2020.html
• https://www.oracle.com/security-alerts/cpuoct2021.html

Affected products (72)

• cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone1:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone10:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone11:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone12:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone13:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone14:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone15:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone16:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone17:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone18:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone19:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone2:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone20:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone21:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone22:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone23:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone24:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone25:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone26:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone27:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone3:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone4:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone5:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone6:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone7:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone8:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:9.0.0:milestone9:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone1:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone2:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone3:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone4:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone5:*:*:*:*:*:*
• cpe:2.3:a:apache:tomcat:10.0.0:milestone6:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
• cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
• cpe:2.3:a:netapp:oncommand_system_manager:*:*:*:*:*:*:*:*
• cpe:2.3:o:opensuse:leap:15.1:*:*:*:*:*:*:*
• cpe:2.3:o:opensuse:leap:15.2:*:*:*:*:*:*:*
• cpe:2.3:o:canonical:ubuntu_linux:16.04:*:*:*:esm:*:*:*

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