CVE-2025-12972
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 · uneditedFluent Bit out_file plugin does not properly sanitize tag values when deriving output file names. When the File option is omitted, the plugin uses untrusted tag input to construct file paths. This allows attackers with network access to craft tags containing path traversal sequences that cause Fluent Bit to write files outside the intended output directory.
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 confidenceThe Fluent Bit out_file plugin uses untrusted tag values to derive output file names when the File option is omitted. An attacker with network access can craft tags containing path traversal sequences (e.g., ../../etc/passwd) to write arbitrary files outside the intended output directory.
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= 4.1.0CVSS 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
- None
- Integrity
- Low
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/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 Fluent Bit installation and versionRun 'fluent-bit --version' or check the package manager (dpkg -l, rpm -qi fluent-bit) to determine the installed versionAffected if The version is Treasuredata Fluent Bit 4.1.0
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Locate Fluent Bit configuration filesSearch for fluent-bit.conf, *.conf files in /etc/fluent/, or configuration directories used by your deploymentAffected if Configuration files exist and the out_file plugin is referenced
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Verify out_file plugin usageIn the configuration files, look for [OUTPUT] sections with 'Name file' or 'Name out_file' without an explicit 'File' parameterAffected if The out_file plugin is configured without a File option, causing tag-derived filenames
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Check tag input sourcesExamine INPUT sections that feed into the out_file output, particularly [INPUT] entries with 'Name tail', 'Name tcp', 'Name syslog', or similar network-based inputsAffected if Network-accessible inputs can receive tags from untrusted sources without validation
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Inspect tag format and validationLook for filter configurations (particularly [FILTER] with Name modify, Name parser, or Lua) that process tags, or any application-layer tag validation before the out_file pluginAffected if Tags are passed directly to out_file without filtering path traversal sequences (..) or absolute path characters
You are affected if running Treasuredata Fluent Bit 4.1.0 with the out_file plugin configured without an explicit File option, allowing untrusted network sources to inject tags with path traversal sequences.
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 dataConfigure explicit File options in the out_file plugin to prevent tag-derived filenames, or implement input validation to reject tags containing path traversal sequences such as ../ or absolute paths.
- Consultation4.0 h
- Implementation8.0 h
- Testing4.0 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 $5,120.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-12972 — 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-2025-12972 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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