What’s Vulnerable › Vulnerabilities
CVE-2021-30639: DoS after non-blocking IO error
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 6.9% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2021-07-12 · updated 2026-06-17
- Weakness: CWE-755
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 products
- Apache Tomcat: 8.5.64, 9.0.44, 10.0.3, 10.0.4
- McAfee,LLC McAfee ePolicy Orchestrator (ePO): before 5.10.0; 5.10.0, 5.10.0-update_1, 5.10.0-update_10, 5.10.0-update_2, 5.10.0-update_3, 5.10.0-update_4 (+5) — fixed in 5.10.0
- Oracle Big Data Spatial And Graph: before 23.1 — fixed in 23.1
How to fix
Upgrade to a fixed version: McAfee,LLC McAfee ePolicy Orchestrator (ePO) 5.10.0; Oracle Big Data Spatial And Graph 23.1. Check the vendor advisory for mitigations.
References
- https://kc.mcafee.com/corporate/index?page=content&id=SB10366
- https://lists.apache.org/thread.html/r79a7c019712b39aedf7cf4da9276d80610f04441b2a4f6506cb2daaf%40%3Cdev.tomcat.apache.org%3E
- https://lists.apache.org/thread.html/r79a7c019712b39aedf7cf4da9276d80610f04441b2a4f6506cb2daaf%40%3Cusers.tomcat.apache.org%3E
- https://lists.apache.org/thread.html/rd84fae1f474597bdf358f5bdc0a5c453c507bd527b83e8be6b5ea3f4%40%3Cannounce.tomcat.apache.org%3E
- https://security.gentoo.org/glsa/202208-34
- https://security.netapp.com/advisory/ntap-20210827-0007/
- https://www.oracle.com/security-alerts/cpujan2022.html
- https://kc.mcafee.com/corporate/index?page=content&id=SB10366
- https://lists.apache.org/thread.html/r79a7c019712b39aedf7cf4da9276d80610f04441b2a4f6506cb2daaf%40%3Cdev.tomcat.apache.org%3E
- https://lists.apache.org/thread.html/r79a7c019712b39aedf7cf4da9276d80610f04441b2a4f6506cb2daaf%40%3Cusers.tomcat.apache.org%3E
- https://lists.apache.org/thread.html/rd84fae1f474597bdf358f5bdc0a5c453c507bd527b83e8be6b5ea3f4%40%3Cannounce.tomcat.apache.org%3E
- https://security.gentoo.org/glsa/202208-34
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