An icinga2 security update has been released for Debian GNU/Linux 9 LTS.

DLA 2816-1: icinga2 security update

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Debian LTS Advisory DLA-2816-1 debian-lts@lists.debian.org
  https://www.debian.org/lts/security/ Sylvain Beucler
November 10, 2021   https://wiki.debian.org/LTS
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Package : icinga2
Version : 2.6.0-2+deb9u2
CVE ID : CVE-2021-32739 CVE-2021-32743 CVE-2021-37698
Debian Bug : 991494

Several vulnerabilities were discovered in Icinga 2, a general-purpose
monitoring application. An attacker could retrieve sensitive
information such as service passwords and ticket salt by querying the
web API, or by intercepting unsufficiently checked encrypted
connections.

CVE-2021-32739

A vulnerability exists that may allow privilege escalation for
authenticated API users. With a read-ony user's credentials, an
attacker can view most attributes of all config objects including
`ticket_salt` of `ApiListener`. This salt is enough to compute a
ticket for every possible common name (CN). A ticket, the master
node's certificate, and a self-signed certificate are enough to
successfully request the desired certificate from Icinga. That
certificate may in turn be used to steal an endpoint or API user's
identity. See also complementary manual procedures:
  https://icinga.com/blog/2021/07/15/releasing-icinga-2-12-5-and-2-11-10/#change-ticket-salt
  https://icinga.com/blog/2021/07/15/releasing-icinga-2-12-5-and-2-11-10/#replace-icinga-ca

CVE-2021-32743

Some of the Icinga 2 features that require credentials for
external services expose those credentials through the API to
authenticated API users with read permissions for the
corresponding object types. IdoMysqlConnection and
IdoPgsqlConnection exposes the password of the user used to
connect to the database. An attacker who obtains these credentials
can impersonate Icinga to these services and add, modify and
delete information there. If credentials with more permissions are
in use, this increases the impact accordingly.

CVE-2021-37698

InfluxdbWriter and Influxdb2Writer do not verify the server's
certificate despite a certificate authority being
specified. Icinga 2 instances which connect to any of the
mentioned time series databases (TSDBs) using TLS over a spoofable
infrastructure should immediately upgrade. Such instances should
also change the credentials (if any) used by the TSDB writer
feature to authenticate against the TSDB.

For Debian 9 stretch, these problems have been fixed in version
2.6.0-2+deb9u2.

We recommend that you upgrade your icinga2 packages.

For the detailed security status of icinga2 please refer to
its security tracker page at:
  https://security-tracker.debian.org/tracker/icinga2

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