Several vulnerabilities have been discovered in netty-3.9, a Java NIO client/server socket framework.
Netty before 4.1.42.Final mishandles whitespace before the colon in HTTP headers (such as a "Transfer-Encoding : chunked" line), which leads to HTTP request smuggling.
HttpObjectDecoder.java in Netty before 4.1.44 allows an HTTP header that lacks a colon, which might be interpreted as a separate header with an incorrect syntax, or might be interpreted as an "invalid fold."
HttpObjectDecoder.java in Netty before 4.1.44 allows a Content-Length header to be accompanied by a second Content-Length header, or by a Transfer-Encoding header.
For Debian 9 stretch, these problems have been fixed in version 3.9.9.Final-1+deb9u1.
We recommend that you upgrade your netty-3.9 packages.
For the detailed security status of netty-3.9 please refer to its security tracker page at: https://security-tracker.debian.org/tracker/netty-3.9
Further information about Debian LTS security advisories, how to apply these updates to your system and frequently asked questions can be found at: https://wiki.debian.org/LTS