Remote denial of service in Apache Tomcat

Published: 2021-07-29
Risk Medium
Patch available YES
Number of vulnerabilities 1
CVE-ID CVE-2021-30639
Exploitation vector Network
Public exploit N/A
Vulnerable software
Apache Tomcat
Server applications / Web servers

Vendor Apache Foundation

Security Bulletin

This security bulletin contains one medium risk vulnerability.

1) Improper Handling of Exceptional Conditions

EUVDB-ID: #VU55422

Risk: Medium


CVE-ID: CVE-2021-30639

CWE-ID: CWE-755 - Improper Handling of Exceptional Conditions

Exploit availability: No


The vulnerability allows a remote attacker to perform a denial of service (DoS) attack.

The vulnerability exists due to improper error management within the application when handling unexpected connection termination. A remote attacker can drop connection with the Apache Tomcat server, which triggers a non-blocking I/O error and causes all requests, handled by that request object, to fail. As a result, a remote attacker can initiate and drop connections to the server and perform a denial of service attack.


Install updates from vendor's website.

Vulnerable software versions

Apache Tomcat: 10.0.0 - 10.0.4, 9.0.0 - 9.0.44, 8.5.0 - 8.5.64

CPE2.3 External links

Q & A

Can this vulnerability be exploited remotely?

How the attacker can exploit this vulnerability?

Is there known malware, which exploits this vulnerability?