Path Traversal Flaw Hits IBM Langflow

A security vulnerability identified as CVE-2026-8859 has been disclosed in IBM Langflow OSS, impacting versions 1.0.0 through 1.10.0. The flaw resides in the platform's APIRequest component, creating a potential pathway for attackers to manipulate file storage locations.

Understanding the Input Validation Defect

The issue stems from a failure to sanitize input during specific operations. When the "Save to File" feature is active, the software processes filenames extracted from HTTP response Content-Disposition headers. Because these filenames are not properly validated before being combined with the temporary directory path, the application is susceptible to path traversal sequences.

Mechanism for File Manipulation

An attacker who controls an external HTTP server can exploit this by supplying crafted filename values that include sequences such as ../. By doing so, the attacker can influence the software to write files into unintended, arbitrary locations that are accessible to the Langflow process. This process relies on the lack of sanitization within the APIRequest component to execute the unauthorized write action.

Vulnerability Metrics and Impact

The severity of this finding is categorized as follows:

• Advisory ID: GHSA-mvq6-wcf9-wpxf
• Vulnerability: CVE-2026-8859
• Severity: critical (CVSS 9.9)
• Affected Versions: 1.0.0 through 1.10.0

Implications for System Integrity

The identification of a CVSS 9.9 vulnerability underscores the stakes for environments deploying IBM Langflow OSS. Because the flaw allows for writing files to arbitrary locations, it represents a significant challenge to the expected file-handling security boundaries of the application. Organizations utilizing this software should evaluate their exposure, particularly where the "Save to File" feature is utilized in production workflows, as the vulnerability directly relies on this specific configuration to bypass standard directory restrictions.