A ruby-rack-cors security update has been released for Debian GNU/Linux 9 LTS to address a directory traversal issue.

DLA 2389-1: ruby-rack-cors security update

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Debian LTS Advisory DLA-2389-1 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 : ruby-rack-cors
Version : 0.4.0-1+deb9u2
CVE ID : CVE-2019-18978
Debian Bug : 944849

This package allowed ../ directory traversal to access private
resources because resource matching did not ensure that
pathnames were in a canonical format.

For Debian 9 stretch, this problem has been fixed in version
0.4.0-1+deb9u2.

We recommend that you upgrade your ruby-rack-cors packages.

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

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