CVE-2026-6596: Langflow Denial of Service Vulnerability

MODERATE
Advisory Identifier: GHSA-vvfc-fp59-m92g
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CVSS 7.3
CWE-284
Published
Advisory Summary

CVE-2026-6596 is a MODERATE (CVSS 7.3) denial of service vulnerability (CWE-284: Improper Access Control) affecting Langflow libraries in the PyPI ecosystem. The issue involves dos through lack of file size restriction via deprecated unauthenticated file upload api. Remediation is available by upgrading affected packages to version 0.9.1.

CVE-2026-6596 at a Glance

CVE Identifier CVE-2026-6596
GHSA Identifier GHSA-vvfc-fp59-m92g
Severity MODERATE
CVSS v3.1 Base Score 7.3
CWE Classification CWE-284: Improper Access Control
Affected Product Langflow
Package Ecosystem PyPI
Published Date
Last Updated

Security Impact

CVSS: 7.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity Low (I:L)
Availability Low (A:L)

How to Fix CVE-2026-6596

To remediate this vulnerability, upgrade all affected Langflow dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

langflow-base fixed: 0.9.1 
pip install langflow-base>=0.9.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

pip show langflow-base

How to Check if You Are Affected

To determine whether your Python environment is affected by CVE-2026-6596, inspect your installed packages using pip:

pip show langflow-base

Analyze the terminal output to locate any version of Langflow in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 0.9.1), your application is affected.

Note: The pip show langflow-base command checks currently installed packages in your active Python environment.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-284: Improper Access Control, where the product does not restrict or incorrectly restricts access to a resource from an unauthorized actor. In Langflow, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

A security flaw has been discovered in langflow-ai langflow up to 1.1.0. This issue affects the function create_upload_file of the file src/backend/base/Langflow/api/v1/endpoints.py of the component API Endpoint. The manipulation results in unrestricted upload. It is possible to launch the attack remotely. The exploit has been released to the public and may be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.

CVE-2026-6596 Affected Langflow Versions

1 component(s)
Fixed Versions:
0.9.1
Product / Package Ecosystem Affected Versions Fixed Version
langflow-base
pypi/langflow-base
PyPI
< 0.9.1
0.9.1

References

NVD — CVE-2026-6596 NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-6596
Security Fix Commit FIX COMMIT
https://github.com/langflow-ai/langflow/commit/b5662446bc8c54d928e278d3d26ad95b62425815
Langflow Source Repository REPOSITORY
https://gist.github.com/chenhouser2025/c2aabfdee41009cfe45d28a9924742a0
Langflow Source Repository REPOSITORY
https://github.com/langflow-ai/langflow
Langflow Source Repository REPOSITORY
https://github.com/langflow-ai/langflow/commits/v1.9.1
vuldb.com/submit/791919 WEB
https://vuldb.com/submit/791919
vuldb.com/vuln/358231 WEB
https://vuldb.com/vuln/358231
vuldb.com/vuln/358231/cti WEB
https://vuldb.com/vuln/358231/cti

Frequently Asked Questions

What is CVE-2026-6596?
CVE-2026-6596 is a security vulnerability in Langflow involving DoS Through Lack of File Size Restriction via Deprecated Unauthenticated File Upload API under CWE-284: Improper Access Control.
Which Langflow versions are affected?
Affected versions include releases prior to 0.9.1 across affected packages: langflow-base.
What version fixes CVE-2026-6596?
Upgrading to 0.9.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is langflow-base affected?
Yes, langflow-base is affected in releases prior to 0.9.1. Upgrade your dependency to 0.9.1 or later.
What is the CVSS score of CVE-2026-6596?
CVE-2026-6596 has a CVSS v3.1 base score of 7.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L.
What CWE is associated with CVE-2026-6596?
CVE-2026-6596 is classified under CWE-284: Improper Access Control (The product does not restrict or incorrectly restricts access to a resource from an unauthorized actor.).
How can I check PyPI dependencies for CVE-2026-6596?
Run the dependency tree command: 'pip show langflow-base'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-vvfc-fp59-m92g",
  "modified" : "2026-06-18T17:59:34Z",
  "published" : "2026-04-20T03:34:42Z",
  "aliases" : [ "CVE-2026-6596" ],
  "summary" : "Langflow: DoS Through Lack of File Size Restriction via Deprecated Unauthenticated File Upload API",
  "details" : "A security flaw has been discovered in langflow-ai langflow up to 1.1.0. This issue affects the function create_upload_file of the file src/backend/base/Langflow/api/v1/endpoints.py of the component API Endpoint. The manipulation results in unrestricted upload. It is possible to launch the attack remotely. The exploit has been released to the public and may be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:L"
  }, {
    "type" : "CVSS_V4",
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  } ],
  "affected" : [ {
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      "ecosystem" : "PyPI",
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    },
    "ranges" : [ {
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      }, {
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      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
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  }, {
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    "url" : "https://vuldb.com/submit/791919"
  }, {
    "type" : "WEB",
    "url" : "https://vuldb.com/vuln/358231"
  }, {
    "type" : "WEB",
    "url" : "https://vuldb.com/vuln/358231/cti"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-284" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2026-04-24T20:13:26Z",
    "nvd_published_at" : "2026-04-20T03:16:16Z"
  }
}