CVE-2021-30639

CVE-2021-30639: vulnerability in Apache Tomcat

DoS after non-blocking IO error

Published · Updated

Follow this CVE+ Monitor Apache Tomcat+ Monitor org.apache.tomcat:tomcat

E-mail alert when it lands in KEV, gets a public PoC or its score goes up.

3Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackepss 6.9%
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.
Affected products
Apache Software Foundation · Apache Tomcat
Related CVEs — Apache Tomcat

In the same product, most dangerous first.

CVE-2017-12617HIGHCVE-2017-12617EPSS 100.0%KEVCVE-2025-24813CRITICALApache Tomcat: Potential RCE and/or information disclosure and/or information corruption with partial PUTEPSS 99.9%KEVCVE-2017-12615HIGHCVE-2017-12615EPSS 99.7%KEVCVE-2026-34486HIGHApache Tomcat: Fix for CVE-2026-29146 allowed bypass of EncryptInterceptorEPSS 98.5%KEVCVE-2016-8735CRITICALCVE-2016-8735EPSS 90.3%KEVCVE-2018-11784—CVE-2018-11784EPSS 97.7%