CVE-2026-48545 describes a cookie injection vulnerability in Gradio before version 6.15.0. The issue arises because a shared module-level HTTP client used in the reverse proxy endpoint stores a parent-domain cookie injected by an attacker controlling any HF Space. This cookie is then automatically replayed in subsequent proxy requests to other legitimate Spaces, enabling cross-Space session fixation that impacts all users on the same Gradio deployment. This vulnerability allows attackers to manipulate session cookies across different Spaces, potentially compromising user sessions.

The vulnerability enables remote attackers to perform cross-Space session fixation by injecting and replaying cookies across different Spaces within the same Gradio deployment. This can lead to unauthorized session manipulation affecting all users of the vulnerable deployment. The CVSS 4.0 score of 7.6 indicates a high severity impact with network attack vector, high complexity, no privileges required, and user interaction needed.

Patch status is not yet confirmed — check the vendor advisory for current remediation guidance. Since no official fix or remediation level is provided, users should monitor the vendor's communications for updates. Until a patch is available, consider restricting access to the reverse proxy endpoint or isolating Spaces to limit cross-Space cookie sharing.