CVE-2026-56671 is a path traversal vulnerability in ComfyUI versions prior to 0.28.0 affecting the get_model_preview function in app/model_manager.py. The vulnerability allows unauthenticated remote attackers to read image-decodable files outside the intended model directory by supplying unsanitized filenames including literal ../, percent-encoded traversal sequences, or absolute paths via an unrestricted route capture. The path was constructed using os.path.join(folder, filename) without any containment check, and the path_index parameter was also unbounded, enabling host path enumeration via error messages. Disclosed files are limited to those decodable by Pillow (re-encoded as WEBP), but the bug also serves as a file-existence oracle and leaks internal path information. The issue has been patched in ComfyUI version 0.28.0. Users are strongly advised to upgrade immediately to mitigate unauthorized file disclosure risks.