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Vulnerability record · CVE-2021-42340 · published 14 October 2021

CVE-2021-42340: Apache tomcat vulnerability

Apache · Tomcat

The fix for bug 63362 present in Apache Tomcat 10.1.0-M1 to 10.1.0-M5, 10.0.0-M1 to 10.0.11, 9.0.40 to 9.0.53 and 8.5.60 to 8.5.71 introduced a memory leak. The object introduced to collect metrics for HTTP upgrade connections was not released for WebSocket connections once the connection was closed. This created a memory leak that, over time, could lead to a denial of service via an OutOfMemoryError.

7.5 CVSS 3.1 High EPSS 12% · top 4.1% CWE-772 · CWE-772
7.5CVSS 3.1 base score, v2 5.0
12%EPSS exploitation probability, 30 days
NoNot in CISA KEV
18Affected product versions listed by NVD
18References
17 Jun 2026Last modified by NVD

Description

The fix for bug 63362 present in Apache Tomcat 10.1.0-M1 to 10.1.0-M5, 10.0.0-M1 to 10.0.11, 9.0.40 to 9.0.53 and 8.5.60 to 8.5.71 introduced a memory leak. The object introduced to collect metrics for HTTP upgrade connections was not released for WebSocket connections once the connection was closed. This created a memory leak that, over time, could lead to a denial of service via an OutOfMemoryError.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

18 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://kc.mcafee.com/corporate/index?page=content&id=SB10379 Third Party Advisory
https://lists.apache.org/thread.html/r8097a2d1550aa78e585fc77e602b9046e6d4099d8d132497c5387784%40%3Ccommits.myfaces.apac
https://lists.apache.org/thread.html/r83a35be60f06aca2065f188ee542b9099695d57ced2e70e0885f905c%40%3Cannounce.tomcat.apac Mailing ListVendor Advisory
https://security.gentoo.org/glsa/202208-34 Third Party Advisory
https://security.netapp.com/advisory/ntap-20211104-0001/ Third Party Advisory
https://www.debian.org/security/2021/dsa-5009 Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpujul2022.html PatchThird Party Advisory
https://kc.mcafee.com/corporate/index?page=content&id=SB10379 Third Party Advisory
https://lists.apache.org/thread.html/r8097a2d1550aa78e585fc77e602b9046e6d4099d8d132497c5387784%40%3Ccommits.myfaces.apac
https://lists.apache.org/thread.html/r83a35be60f06aca2065f188ee542b9099695d57ced2e70e0885f905c%40%3Cannounce.tomcat.apac Mailing ListVendor Advisory
https://security.gentoo.org/glsa/202208-34 Third Party Advisory
https://security.netapp.com/advisory/ntap-20211104-0001/ Third Party Advisory
https://www.debian.org/security/2021/dsa-5009 Third Party Advisory
https://www.oracle.com/security-alerts/cpuapr2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpujan2022.html PatchThird Party Advisory
https://www.oracle.com/security-alerts/cpujul2022.html PatchThird Party Advisory

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Source: NIST National Vulnerability Database (record CVE-2021-42340), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.