CVE-2021-30639

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.

How to fix CVE-2021-30639

To remediate CVE-2021-30639, upgrade the affected package to a fixed version below.

• —upgrade to 8.5.65 or later
• —upgrade to 10.0.5 or later

Is CVE-2021-30639 being exploited?

Low — EPSS is 0.4%, meaning exploitation activity has not been observed at scale.

Affected packages (2)

• >= 8.5.64, < 8.5.65, >= 9.0.44, < 9.0.45, >= 10.0.3, < 10.0.4, >= 10.0.4, < 10.0.5
• >= 10.0.3, < 10.0.5

CVSS scores

References (11)

• ADVISORYnvd.nist.gov/vuln/detail/CVE-2021-30639
• WEBkc.mcafee.com/corporate/index?page=content&id=SB10366
• WEBlists.apache.org/thread.html/r79a7c019712b39aedf7cf4da9276d80610f04441b2a4f6506cb2daaf@%3Cdev.tomcat.apache.org%3E
• WEBlists.apache.org