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CVE-2026-121458— Instatic before 0.0.21 Authorization Bypass via MCP Content Read Tools

Quick assessment

Affected
CoreBunch Instatic
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Instatic 0.0.21 之前的版本在其 AI/MCP 内容读取工具中存在一个缺少授权检查的漏洞。该漏洞允许拥有 和 权限的低特权已认证用户，通过调用 和 接口，绕过正常 HTTP API 所实施的细粒度对象级授权检查，从而访问属于其他用户的数据行。攻击者可利用 MCP 接口获取私密或未发布的草稿内容，并枚举帖子系统表中的数据行，导致跨用户数据泄露。

CVSS 6.5 · Medium
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I. Basic Information for CVE-2026-121458

Vulnerability Information
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Vulnerability Title
Instatic before 0.0.21 Authorization Bypass via MCP Content Read Tools
Source: CVE Program / CVE List V5
Vulnerability 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 Attackers can use the MCP interface to retrieve private or unpublished draft content and enumerate rows from the posts system table, resulting in cross-user data disclosure.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
授权机制缺失
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
CoreBunch Instatic 0.0.12 ~ 0.0.21 -

II. Public POCs for CVE-2026-121458

# POC Description Source Link Shenlong Link
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III. Intelligence Information for CVE-2026-121458

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Other References for CVE-2026-121458 (3)

IV. Related Vulnerabilities

Same product: Instatic
Same vendor: CoreBunch
Same weakness: CWE-862