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CVE Record

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.

HighCVSS 7.5Not KEV-listedUpdated
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Glexia's TakeAutomated analysishigh

Security readout for executives and security teams

Plain-English summary

Icinga 2 could send monitoring data to certain back-end databases over TLS without properly checking the server certificate. An attacker able to spoof or intercept that connection could read sensitive monitoring data or credentials. Upgrade is the only named workaround-free fix.

Executive priority

Treat as high priority where monitoring data or TSDB credentials cross shared, cloud, or otherwise spoofable networks. The issue is narrower than an internet-wide remote takeover, but the named confidentiality impact and lack of workaround justify prompt patching.

Technical view

CVE-2021-37698 is CWE-295 in Icinga 2.5.0 through 2.13.0. ElasticsearchWriter, GelfWriter, InfluxdbWriter, and Influxdb2Writer failed to validate the TLS service certificate even when a CA was configured. Fixed versions are 2.13.1, 2.12.6, and 2.11.11.

Likely exposure

Exposure is limited to Icinga 2 deployments using the named writer features over TLS, especially across spoofable or untrusted network paths. Systems not using those TSDB writer integrations are not indicated as affected by the provided sources.

Exploitation context

The provided sources do not show CISA KEV listing or active exploitation. Practical abuse would require a position to spoof or intercept the TLS connection between Icinga and the target TSDB service.

Researcher notes

The core issue is certificate validation failure, not TLS absence. Scope should be validated by feature usage and network path. Sources provide fixed release versions and credential-rotation guidance, but no evidence of active exploitation, public exploit tooling, or non-upgrade workaround.

Mitigation direction

  • Upgrade affected Icinga 2 instances to 2.13.1, 2.12.6, 2.11.11, or later.
  • Rotate any credentials used by affected TSDB writer features.
  • Prioritize systems sending writer traffic over untrusted or spoofable infrastructure.
  • Check vendor and distribution advisories for supported package updates.
  • Do not rely on a workaround; sources state none exists aside from upgrading.

Validation and detection

  • Inventory Icinga 2 versions and identify hosts running 2.5.0 through 2.13.0.
  • Review enabled features for ElasticsearchWriter, GelfWriter, InfluxdbWriter, or Influxdb2Writer.
  • Confirm whether those writer connections use TLS and credentials.
  • Verify upgraded packages report a fixed Icinga 2 release line.
  • Confirm TSDB writer credentials were changed after upgrade.
Prepared
Confidence
high
Sources
8

Public sources used

Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.

Potential ATT&CK relevance

Conservative CVE-to-ATT&CK context

These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.

ATT&CK lookup starting points

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cwe · low confidence lookup

CWE-295: Exact CWE lookup

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cve · low confidence lookup

CVE-2021-37698 mapping review

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Vulnerability profileCVE Program record
Severity
High
CVSS
7.5 (3.1)
Known Exploited
No
Published

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Official CVE source material

CNA and ADP enrichment extracted from CVE v5

These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.

1CVSS vectors
0Timeline events
0ADP providers
7Source links

CVSS vector scores

1 official score

We collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.

ScoreVersionSeverityVectorExploitImpactSource
7.5CVSS 3.1HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N3.93.6Primary CVE score

Vulnerability scoring details

Base CVSS 3.1 score

7.5High
CVSS 3.1 vector shape for CVE-2021-37698Attack VectorAttack ComplexityPrivileges RequiredUser InteractionScopeConfidentiality ImpactIntegrity ImpactAvailability Impact

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector
NetworkAdjacentLocalPhysical
Attack Complexity
LowHigh
Privileges Required
NoneLowHigh
User Interaction
NoneRequired
Scope
ChangedUnchanged
Confidentiality Impact
HighLowNone
Integrity Impact
HighLowNone
Availability Impact
HighLowNone

Source materials

Affected products

Products and packages named in the record

VendorProductVersion / packageStatus
Icingaicinga2>= 2.5.0, <= 2.13.0Listed
Weakness

CWE details

CWE-295

CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.

CWE-295 · source CWE mapping

CWE mapping pending import

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