AUGUST 4, 2026
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Case File

CVE-2021-30639

HIGH · CVSS 7.5 EPSS 6.89%

Source: NVD + CISA KEV + EPSS (historical backfill) · Published 2021-07-12 · Last synced 2026-08-04

CyberRota Analysis

This is a high severity vulnerability with a CVSS score of 7.5. It affects Apache. It may be remotely exploitable. It may lead to a denial-of-service condition.

CVE
CVE-2021-30639
Severity
HIGH
CVSS
7.5
EPSS
6.89%
Apache

Original NVD Description

A vulnerability in Apache Tomcat allows an attacker to remotely trigger a denial of service. An error introduced as part of a change to improve error handling during non-blocking I/O meant that the error flag associated with the Request object was not reset between requests. This meant that once a non-blocking I/O error occurred, all future requests handled by that request object would fail. Users were able to trigger non-blocking I/O errors, e.g. by dropping a connection, thereby creating the possibility of triggering a DoS. Applications that do not use non-blocking I/O are not exposed to this vulnerability. This issue affects Apache Tomcat 10.0.3 to 10.0.4; 9.0.44; 8.5.64.

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