Path Traversal in Stable Diffusion WebUI

CVE-2026-77815 affects the Image-to-Image Browser (IIB) extension within Stable Diffusion WebUI. The vulnerability resides in the to_abs_path function located in scripts/iib/tool.py, which utilizes os.path.normpath to normalize file paths. Because os.path.normpath does not resolve symbolic links, the path validation logic (is_path_trusted) can be bypassed. An attacker who can influence the filesystem by creating a symbolic link within a scanned directory can point that link to sensitive files outside the intended root. If the IIB access control feature is enabled - either manually via the IIB_ACCESS_CONTROL environment variable or automatically when the WebUI is launched with network-exposing arguments like --share or --listen - the FileResponse function will follow the symlink and serve the contents of the target file, such as /etc/passwd, to the requester.

Impact

Successful exploitation results in arbitrary local file disclosure of any file readable by the user process running the Stable Diffusion WebUI. This poses a significant risk for server-side information disclosure, potentially exposing configuration files, credentials, or system sensitive data in exposed WebUI deployments.

Recommendation

1. Update the Stable Diffusion WebUI and the Image-to-Image Browser (IIB) extension to the latest version where os.path.realpath has replaced os.path.normpath for path resolution.
2. For deployments where the update is not immediately feasible, ensure IIB_ACCESS_CONTROL is set to 'disable' only if the deployment is fully isolated and does not require file path confinement, or conversely, restrict filesystem write access to the directories scanned by the extension.
3. Audit the filesystem for unauthorized symbolic links within the directories monitored by the IIB extension.