What’s Vulnerable › Vulnerabilities
CVE-2021-41079: Apache Tomcat DoS with unexpected TLS packet
- Severity: high (CVSS 7.5 v3.1)
- Exploited in the wild: not listed in CISA KEV
- EPSS: 7.2% probability of exploitation in the next 30 days
- Public exploit or detection template: none known
- Published: 2021-09-16 · updated 2026-10-08
- Weakness: CWE-20
Description
Apache Tomcat 8.5.0 to 8.5.63, 9.0.0-M1 to 9.0.43 and 10.0.0-M1 to 10.0.2 did not properly validate incoming TLS packets. When Tomcat was configured to use NIO+OpenSSL or NIO2+OpenSSL for TLS, a specially crafted packet could be used to trigger an infinite loop resulting in a denial of service.
Affected products
- Apache Tomcat: from 8.5.0 before 8.5.64; from 9.0.0 before 9.0.44; from 10.0.0 through 10.0.2 — fixed in 8.5.64, 9.0.44
- Debian Linux: 9.0, 10.0, 11.0
- NetApp Management Services For Element Software And Netapp Hci: all versions
How to fix
Upgrade to a fixed version: Apache Tomcat 8.5.64, 9.0.44. Check the vendor advisory for mitigations.
References
- https://lists.apache.org/thread.html/r6b6b674e3f168dd010e67dbe6848b866e2acf26371452fdae313b98a%40%3Cusers.tomcat.apache.org%3E
- https://lists.apache.org/thread.html/rb4de81ac647043541a32881099aa6eb5a23f1b7fd116f713f8ab9dbe%40%3Cdev.tomcat.apache.org%3E
- https://lists.apache.org/thread.html/rccdef0349fdf4fb73a4e4403095446d7fe6264e0a58e2df5c6799434%40%3Cannounce.tomcat.apache.org%3E
- https://lists.debian.org/debian-lts-announce/2021/09/msg00012.html
- https://security.netapp.com/advisory/ntap-20211008-0005/
- https://www.debian.org/security/2021/dsa-4986
- https://lists.apache.org/thread.html/r6b6b674e3f168dd010e67dbe6848b866e2acf26371452fdae313b98a%40%3Cusers.tomcat.apache.org%3E
- https://lists.apache.org/thread.html/rb4de81ac647043541a32881099aa6eb5a23f1b7fd116f713f8ab9dbe%40%3Cdev.tomcat.apache.org%3E
- https://lists.apache.org/thread.html/rccdef0349fdf4fb73a4e4403095446d7fe6264e0a58e2df5c6799434%40%3Cannounce.tomcat.apache.org%3E
- https://lists.debian.org/debian-lts-announce/2021/09/msg00012.html
- https://security.netapp.com/advisory/ntap-20211008-0005/
- https://www.debian.org/security/2021/dsa-4986
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