CRITICAL GRIST-CORE VULNERABILITY ALLOWS RCE ATTACKS VIA SPREADSHEET FORMULAS

Summary from the TLDR InfoSec newsletter

CVE-2026-24002 (CVSS 9.1) is a critical Pyodide sandbox escape vulnerability dubbed "Cellbreak" in Grist-Core that allows attackers to execute arbitrary OS commands or host-runtime JavaScript through malicious spreadsheet formulas. The flaw stems from Grist's blocklist-style sandbox approach that permits traversal through Python's class hierarchy and leaves ctypes available, enabling attackers to access database credentials, API keys, and sensitive files while creating lateral movement opportunities. The vulnerability was patched in version 1.7.9, released January 9, with users advised to update immediately or temporarily mitigate by setting GRIST_SANDBOX_FLAVOR to "gvisor," while avoiding the GRIST_PYODIDE_SKIP_DENO flag that reintroduces the risk.