CVE-2021-25122CWE-200

CVE-2021-25122: vulnerability in Apache Tomcat

Apache Tomcat h2c request mix-up

Published · Updated

Follow this CVE+ Monitor Apache Tomcat+ Monitor tomcat9

E-mail alert when it lands in KEV, gets a public PoC or its score goes up.

8Vexday Risk Score

No sign of exploitation. No public exploitation artifact known so far.

ssvc Trackepss 18%
When responding to new h2c connection requests, Apache Tomcat versions 10.0.0-M1 to 10.0.0, 9.0.0.M1 to 9.0.41 and 8.5.0 to 8.5.61 could duplicate request headers and a limited amount of request body from one request to another meaning user A and user B could both see the results of user A's request.
Affected products
Apache Software Foundation · Apache Tomcat
Related CVEs — Apache Tomcat

In the same product, most dangerous first.

CVE-2017-12617HIGHCVE-2017-12617EPSS 100.0%KEVCVE-2025-24813CRITICALApache Tomcat: Potential RCE and/or information disclosure and/or information corruption with partial PUTEPSS 99.9%KEVCVE-2017-12615HIGHCVE-2017-12615EPSS 99.7%KEVCVE-2026-34486HIGHApache Tomcat: Fix for CVE-2026-29146 allowed bypass of EncryptInterceptorEPSS 98.5%KEVCVE-2016-8735CRITICALCVE-2016-8735EPSS 90.3%KEVCVE-2018-11784—CVE-2018-11784EPSS 97.7%