9.3

CVSS Score

3.1

-

CVSS Score

Basic Information

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CVE-2026-55450

CVE-2026-55450: Langflow: Unauthenticated file upload leads to DoS (space exhaustion) and information leak

Langflow is a tool for building and deploying AI-powered agents and workflows. Prior to 1.9.1, unauthenticated users can upload any amount of data to the server without any limitations. No need for any prior knowledge, only network access to Langflow. This can lead to space exhaustion on the server. In addition, in the response, the absolute path of the uploaded file is reported to the attacker, which is an information leak that can assist in chaining other primitives. This vulnerability is fixed in 1.9.1.

(GitHub Advisory)

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CVE-2026-55450

CVE-2026-55450:

9.3

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

SSVC / BOD 26-04 ↗

Exploitation pocAutomatable YesTech Impact Partial

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Package Name	Ecosystem	Vulnerable Versions	First Patched Version
langflow	pip	< 1.9.1	1.9.1

Technical Details

Vulnerability Intelligence
Miggo AI

Root Cause Analysis

The vulnerability exists in the deprecated POST /api/v1/upload/{flow_id} endpoint, which is handled by the create_upload_file function in src/backend/base/langflow/api/v1/endpoints.py. The advisory and the provided patch clearly indicate that this endpoint lacked authentication. An analysis of the commit 7e5ad32f38f682976a986c9ada23a931e6e1ef97 confirms this. The function signature was changed to include a Depends(get_flow) dependency, which enforces user authentication and authorization, ensuring the user owns the specified flow. Before this change, the function took flow_id as a direct parameter from the URL, with no checks. A second commit, 5b4cd0e4138d4cfd2a8858cab9af745c841ffc85, further mitigates the DoS vector by adding a file size limit, which was also missing in the vulnerable version. Therefore, the create_upload_file function is the exact location of the vulnerability.

Vulnerable functions

create_upload_file

src/backend/base/langflow/api/v1/endpoints.py

The function `create_upload_file` is exposed as an API endpoint `/api/v1/upload/{flow_id}`. Prior to the patch, this endpoint had no authentication. The function signature accepted a `flow_id` directly from the URL without verifying the user's identity or permissions. This allowed any unauthenticated attacker to upload files of arbitrary size, leading to a Denial of Service vulnerability through disk space exhaustion. Additionally, the endpoint's response included the absolute file path of the uploaded file, resulting in an information disclosure vulnerability.

Vulnerability Intelligence
Miggo AI

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WAF Protection Rules

WAF Rule

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Reasoning

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