icinga2: prepare-dirs script allows for symlink attack in the icinga user context (CVE-2020-14004)

An issue was discovered in Icinga2 before v2.12.0-rc1. The prepare-dirs script (run as part of the icinga2 systemd service) executes chmod 2750 /run/icinga2/cmd. /run/icinga2 is under control of an unprivileged user by default. If /run/icinga2/cmd is a symlink, then it will by followed and arbitrary files can be changed to mode 2750 by the unprivileged icinga2 user.

References:

• https://nvd.nist.gov/vuln/detail/CVE-2020-14004
• https://www.openwall.com/lists/oss-security/2020/06/12/1

Patch:

https://github.com/Icinga/icinga2/commit/2f0f2e8c355b75fa4407d23f85feea037d2bc4b6

Affected branches:

• master
• 3.12-stable