CVE-2025-6853
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 · uneditedA vulnerability classified as critical has been found in chatchat-space Langchain-Chatchat up to 0.3.1. This affects the function upload_temp_docs of the file /knowledge_base/upload_temp_docs of the component Backend. The manipulation of the argument flag leads to path traversal. It is possible to initiate the attack remotely. The exploit has been disclosed to the public and may be used.
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 confidenceA path traversal vulnerability exists in the upload_temp_docs function of the Langchain-Chatchat backend API endpoint /knowledge_base/upload_temp_docs. The 'flag' argument is not properly validated, allowing attackers to manipulate file paths using '../' sequences to write files outside the intended upload directory. This can lead to arbitrary file write or overwrite on the server.
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<= 0.3.1CVSS 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
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
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 installed version of Langchain-ChatchatRun version detection command or check package metadata (e.g., pip show chatchat, docker image inspect, or check VERSION file in installation directory)Affected if Version is 0.3.1 or lower (any version <= 0.3.1)
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Locate the upload_temp_docs endpointSearch the codebase for the upload_temp_docs function definition, typically in API route files handling file uploadsAffected if The endpoint exists in the codebase and is accessible via the web API
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Verify the flag parameter accepts path traversal sequencesInspect the upload function code to see if the flag parameter is validated or sanitized before being used in file path operationsAffected if The flag parameter is used directly in file path construction without filtering ../ sequences
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Check if upload_temp_docs endpoint is publicly accessibleReview API routing configuration and authentication settings to determine if the endpoint requires authenticationAffected if Endpoint is exposed without authentication or with weak access controls
You are affected if running Langchain-Chatchat version 0.3.1 or lower AND the upload_temp_docs endpoint is accessible with the flag parameter allowing 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 dataImplement strict input validation on the 'flag' parameter to ensure it contains only allowed characters and resolves to an expected directory. Use os.path.abspath() with directory containment checks, or employ a whitelist approach for permitted upload paths.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA1.0 h
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Free · runs locallyCheck whether your project pulls in CVE-2025-6853 — 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-2025-6853 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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- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
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