CVE-2021-43980 Apache Tomcat: Information disclosure

What is CVE-2021-43980?

CVE-2021-43980 is a low-severity vulnerability in Apache Tomcat, published on 28 Sep 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

The simplified implementation of blocking reads and writes introduced in Tomcat 10 and back-ported to Tomcat 9.0.47 onwards exposed a long standing (but extremely hard to trigger) concurrency bug in Apache Tomcat 10.1.0 to 10.1.0-M12, 10.0.0-M1 to 10.0.18, 9.0.0-M1 to 9.0.60 and 8.5.0 to 8.5.77 that could cause client connections to share an Http11Processor instance resulting in responses, or part responses, to be received by the wrong client.

Weakness: CWE-362

Which versions are affected by CVE-2021-43980?

9 open source packages ship an affected version, including org.apache.tomcat:tomcat and tomcat. It affects 2 products.

Products include Apache Tomcat, Debian Debian Linux.

How do I fix CVE-2021-43980?

Upgrade org.apache.tomcat:tomcat to a fixed version for your release line: 10.0.20, 10.1.0-M14, 8.5.78 or 9.0.62.

Is CVE-2021-43980 being exploited?

There is no known exploitation of CVE-2021-43980 in the wild and no public exploit code.

Other vulnerabilities in Apache Tomcat

• CVE-2025-24813 Apache Tomcat Path Equivalence Exploited Critical 10.0
• CVE-2016-8735 Apache Tomcat Remote Code Execution Exploited Critical 9.8
• CVE-2017-12617 Apache Tomcat Remote Code Execution Exploited High 8.1
• CVE-2017-12615 Apache Tomcat on Windows Remote Code Execution Exploited High 8.1
• CVE-2026-34486 Apache Tomcat Missing Encryption of Sensitive Data Exploited High 7.5

All Apache Tomcat vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as BIT-tomcat-2021-43980, DEBIAN-CVE-2021-43980, GHSA-jx7c-7mj5-9438, SUSE-SU-2022:4009-1, UBUNTU-CVE-2021-43980.