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

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.

Published: 2021-08-19 Last update: 2025-11-03 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-37698 is rated Moderate Risk (55.5/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.42%). EPSS rose +1.26% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-37698

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-06-15 0.17% 1.42% +1.26%
2 2026-01-14 0.14% 0.17% +0.03%
3 2026-01-08 — 0.14% —

Full EPSS history (18 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-37698

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:P/I:N/A:N Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:N)
No availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2021-37698

OS Trackers for CVE-2021-37698

vendor priority summary link
alpine — CVE-2021-37698: 1 source package rows (icinga2); 7 state rows across 7 repos (3.17-community, 3.18-community, 3.19-community, 3.20-community, 3.21-community, 3.22-community, edge-community); fixed 7, open 0. https://security.alpinelinux.org/vuln/CVE-2021-37698
debian not yet assigned CVE-2021-37698 not yet assigned priority: Debian including 1 source packages (icinga2), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 5. https://security-tracker.debian.org/tracker/CVE-2021-37698
gentoo low CVE-2021-37698: 1 GLSA(s) (202412-08), 1 atom(s) (net-analyzer/icinga2); latest impact low. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-37698
suse medium CVE-2021-37698 severity moderate: SUSE including 17 source package names (icinga, icinga2-2.13.1-1.3, …), 18 product×package rows across 4 product lines (SUSE Linux Enterprise Module for HPC 12, SUSE Manager Client Tools Beta for SLE 12, SUSE Manager Client Tools for SLE 12, openSUSE Tumbleweed): Fixed 16, Known Not Affected 2. https://www.suse.com/security/cve/CVE-2021-37698/
ubuntu medium CVE-2021-37698 medium priority: Ubuntu including 1 source packages (icinga2), 15 status rows across 15 suites (bionic, focal, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 6, needs-triage 4, ignored 3, DNE 1, released 1. https://ubuntu.com/security/CVE-2021-37698

Affected software / configurations for CVE-2021-37698

Vendor Product Version Raw CPE
icinga icinga >= 2.5.0, < 2.11.10 cpe:2.3:a:icinga:icinga:*:*:*:*:*:*:*:*
icinga icinga >= 2.12.0, < 2.12.6 cpe:2.3:a:icinga:icinga:*:*:*:*:*:*:*:*
icinga icinga >= 2.13.0, < 2.13.1 cpe:2.3:a:icinga:icinga:*:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*

References for CVE-2021-37698

cvelogic Threat Intelligence