Log in Start free

Vulnerability · Published Jul 12, 2021 · Assigned by apache

CVE-2021-30639DoS after non-blocking IO error

High 7.5

In plain English

A high-severity security flaw in Apache Tomcat from Apache Software Foundation. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 6.9% (higher than 94% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS NVD)7.5High
Exploit odds (30 days)6.9%top 5.9% of all CVEs
Exploited in the wildNo reportsnot in CISA KEV
Attack toolingNoneno public tooling known

Official 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.

Affected packages & fixed versions

EcosystemPackageFixed inAdvisory
Mavenorg.apache.tomcat:tomcat10.0.5GHSA-44qp-qhfv-c7f6
Mavenorg.apache.tomcat:tomcat9.0.45GHSA-44qp-qhfv-c7f6
Mavenorg.apache.tomcat:tomcat8.5.65GHSA-44qp-qhfv-c7f6
Ubuntu:22.04:LTStomcat9no fix listedUBUNTU-CVE-2021-30639
Ubuntu:24.04:LTStomcat9no fix listedUBUNTU-CVE-2021-30639

Affected products (as reported)

VendorProductVersions
Apache Software Foundation Apache Tomcat Apache Tomcat 10 10.0.3 to 10.0.4Apache Tomcat 9 9.0.44Apache Tomcat 8.5 8.5.64

References