CVE-2026-12821 Details

A path traversal vulnerability has been identified in the S3 Document Loader component of FlowiseAI Flowise, affecting versions through 3.1.2. The vulnerability arises from an unknown function in the file packages/components/nodes/documentloaders/S3/S3.ts, where object keys from S3 buckets can be manipulated to traverse directories. This issue can be exploited remotely, allowing attackers to write arbitrary files outside the intended temporary directory used by the loader.

To address this vulnerability, normalize object keys to ensure they are safe basenames or explicitly reject absolute or traversal paths. After constructing the local file path, both the base and target paths should be resolved and checked to ensure the target path is relative to the intended base directory. Additionally, avoid recursive cleanup operations on paths that could be influenced by untrusted object names.