A netty-3.9 security update has been released for Debian GNU/Linux 9 LTS to address several vulnerabilities.

DLA 2365-1: netty-3.9 security update

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Debian LTS Advisory DLA-2365-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Roberto C. Sánchez
September 04, 2020   https://wiki.debian.org/LTS
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Package : netty-3.9
Version : 3.9.9.Final-1+deb9u1
CVE ID : CVE-2019-16869 CVE-2019-20444 CVE-2019-20445
Debian Bug : 941266 950966 950967

Several vulnerabilities have been discovered in netty-3.9, a Java NIO
client/server socket framework.

CVE-2019-16869

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.

CVE-2019-20444

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."

CVE-2019-20445

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