dbcve.org
Fluent BitApplication · Treasuredata

CVE-2025-12969

MEDIUM · 6.5 CVSS v3.1 Published 2025-11-24
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
74/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

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 · unedited
Fluent Bit in_forward input plugin does not properly enforce the security.users authentication mechanism under certain configuration conditions. This allows remote attackers with network access to the Fluent Bit instance exposing the forward input to send unauthenticated data. By bypassing authentication controls, attackers can inject forged log records, flood alerting systems, or manipulate routing decisions, compromising the authenticity and integrity of ingested logs.

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 confidence

Fluent Bit's in_forward input plugin fails to properly enforce the security.users authentication mechanism under certain configuration conditions, allowing remote attackers with network access to send unauthenticated data. This bypass enables injection of forged log records, alerting system flooding, and manipulation of log routing decisions.

MitigationReview and correct the in_forward plugin configuration to ensure security.users authentication is properly enforced; verify that network exposure is minimized and consider network segmentation as a compensating control.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

NVD · CPE data
Fluent BitApplication
Affected:= 4.1.0

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
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
Low
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify Fluent Bit version
    Run 'fluent-bit --version' or check the installed package version (e.g., dpkg -l | grep fluent-bit, rpm -qi fluent-bit)
    Affected if Version is 4.1.0 from Treasuredata distribution
  2. Confirm in_forward plugin is enabled
    Search Fluent Bit configuration files (*.conf) for 'Input' or '@IN' sections containing 'in_forward' - check /etc/fluent-bit/fluent-bit.conf and any conf.d includes
    Affected if in_forward input plugin is configured and loaded
  3. Verify security.users is configured
    Search Fluent Bit configuration for 'security.users' or 'HTTP_Auth' entries in [security] sections, or check if security plugin is loaded via 'fluent-bit -i' list
    Affected if security.users authentication is NOT configured or is missing entirely
  4. Check in_forward configuration for authentication bypass conditions
    Review in_forward plugin configuration block for 'auth' or 'allow_duplicated_keys' parameters, and verify if network listener is bound to 0.0.0.0 or exposed interface without authstrict mode
    Affected if in_forward is exposed to network (0.0.0.0) without proper authstrict setting or security.users is not enforced on that listener

User is affected if running Treasuredata Fluent Bit 4.1.0 with in_forward plugin enabled and exposed to network without properly enforced security.users authentication configuration

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Review and correct the in_forward plugin configuration to ensure security.users authentication is properly enforced; verify that network exposure is minimized and consider network segmentation as a compensating control.

Recommended fix Moderate confidence

4.1.1 or later stable release

  1. 1. Identify current Fluent Bit version using 'fluent-bit --version'
  2. 2. Download the latest stable Fluent Bit release from the official releases page (https://releases.fluentbit.io)
  3. 3. Backup current Fluent Bit configuration files
  4. 4. Install the updated version (preferably 4.1.1 or later)
  5. 5. Restart Fluent Bit service
  6. 6. Verify the security.users authentication is properly enforced by testing the in_forward endpoint
Caveat Review release notes for any configuration changes between 4.1.0 and the target version

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Fluent Bit Scoped from the published advisory
  • Consultation3.0 h
  • Implementation6.0 h
  • Testing4.0 h
  • Review / QA2.0 h
15.0 hours of engineering $2,640
Get help mitigating

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,224.

Scan for this in your stack

Free · runs locally
dbcve dependency scanner

Check whether your project pulls in CVE-2025-12969 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.

Get it on GitHub Scan in the browser

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2025-12969 in production — separate from our analysis above.

No notes yet

Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.

What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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
  • No spam, self-promotion, credentials, or personal data