A ruby2.3 security update has been released for Debian GNU/Linux 9 LTS to address an issue where an attacker can smuggle a request.

DLA 2391-1: ruby2.3 security update

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Debian LTS Advisory DLA-2391-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Utkarsh Gupta
October 01, 2020   https://wiki.debian.org/LTS
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Package : ruby2.3
Version : 2.3.3-1+deb9u9
CVE ID : CVE-2020-25613

A potential HTTP request smuggling vulnerability in WEBrick
was reported.

WEBrick (bundled along with ruby2.3) was too tolerant against
an invalid Transfer-Encoding header. This may lead to
inconsistent interpretation between WEBrick and some HTTP proxy
servers, which may allow the attacker to “smuggle” a request.

For Debian 9 stretch, this problem has been fixed in version
2.3.3-1+deb9u9.

We recommend that you upgrade your ruby2.3 packages.

For the detailed security status of ruby2.3 please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/ruby2.3

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