CVE-2025-37730
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedImproper certificate validation in Logstash's TCP output could lead to a man-in-the-middle (MitM) attack in “client” mode, as hostname verification in TCP output was not being performed when the ssl_verification_mode => full was set.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceLogstash's TCP output plugin fails to perform hostname verification when ssl_verification_mode is set to 'full' in client mode, allowing SSL/TLS certificates to be accepted without proper validation and enabling man-in-the-middle attacks.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:L/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Logstash installation and versionRun command: logstash --version or check installed package version via system package manager (dpkg -i, rpm -qi, etc.)Affected if Installed version falls within the vulnerable version range for Logstash and contains the TCP output plugin
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Locate TCP output plugin configurationSearch Logstash pipeline configuration files (*.conf) in /etc/logstash/conf.d/ or custom config directories for 'tcp' output plugin usageAffected if A TCP output block is defined in any Logstash pipeline configuration
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Verify SSL/TLS is enabled for TCP outputInspect the TCP output configuration block for ssl => true or ssl_enabled => true parameterAffected if SSL/TLS is explicitly enabled on the TCP output endpoint
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Check ssl_verification_mode settingInspect the TCP output configuration for 'ssl_verification_mode' parameter - look for value 'full'Affected if ssl_verification_mode is explicitly set to 'full' within the TCP output configuration
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Confirm client mode configurationExamine TCP output settings for client mode indicators such as 'client_mode => true', 'mode => client', or peer role configuration indicating this Logstash instance acts as SSL clientAffected if The TCP output plugin is configured to operate in client mode (initiating connections to another SSL endpoint)
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Review certificate verification behaviorIf possible, test actual SSL handshake behavior or examine debug logs (set debug => true or LOG_LEVEL=debug) to observe if hostname verification occurs during SSL handshakeAffected if SSL handshake completes without hostname verification errors despite ssl_verification_mode => full being set in client mode
Environment is affected if Logstash TCP output plugin is in use with SSL enabled, ssl_verification_mode set to 'full', and operating in client mode - the combination that bypasses hostname verification.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataReview and update Logstash to the latest version when a patch is released, and verify that proper certificate validation is functioning as expected in affected TCP output configurations.
- Consultation3.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $3,408.
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Free · runs locallyCheck whether your project pulls in CVE-2025-37730 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-37730 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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