CVE-2019-17569
MediumCVSS 4.8Exploitation Probability (EPSS)
Very high risk95th percentile - higher than 95% of all known CVEs
Summary
Apache Tomcat versions 9.0.28 to 9.0.30, 8.5.48 to 8.5.50, and 7.0.98 to 7.0.99 contain a regression that causes invalid Transfer-Encoding headers to be incorrectly processed, leading to a possibility of HTTP Request Smuggling if Tomcat is behind a reverse proxy that incorrectly handles the invalid Transfer-Encoding header in a particular manner.
Risk Assessment
The risk is the possibility of a request smuggling attack, which could lead to bypassing security controls, intercepting requests, or attacks on other users.
Recommendation
Update Apache Tomcat to a patched version. Also, configure reverse proxies securely to avoid issues with Transfer-Encoding headers.
Original NVD description (English source)
The refactoring present in Apache Tomcat 9.0.28 to 9.0.30, 8.5.48 to 8.5.50 and 7.0.98 to 7.0.99 introduced a regression. The result of the regression was that invalid Transfer-Encoding headers were incorrectly processed leading to a possibility of HTTP Request Smuggling if Tomcat was located behind a reverse proxy that incorrectly handled the invalid Transfer-Encoding header in a particular manner. Such a reverse proxy is considered unlikely.