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Medium · 6.5 CVE-2026-121458 EUVD-2026-115812GHSA-wq53-554h-vq3f

Instatic before 0.0.21 Authorization Bypass via MCP Content Read Tools

Published Nov 3, 2026 · Updated Nov 8, 2026 · Assigned by VulnCheck

Description

Instatic before 0.0.21 contains a missing authorization vulnerability in its AI/MCP content read tools that allows low-privileged authenticated users with ai.chat and content.edit.own capabilities to access data rows belonging to other users by calling content_get_document and content_list_documents without the object-level authorization checks enforced by the normal HTTP API. Attackers can use the MCP interface to retrieve private or unpublished draft content and enumerate rows from the posts system table, resulting in cross-user data disclosure.

Affected products

VendorProductAffectedFixed
CoreBunch Instatic 0.0.12 – < 0.0.21 0.0.21

References