# CVE-2026-121458: Instatic authorization bypass in AI/MCP content read tools

Source: https://junglewise.ai/threats/cve-2026-121458-instatic-before-0-0-21-contains-a-missing-authorization  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-11-03. Updated: 2026-11-03  
License: CC BY 4.0 with a link back

CVE-2026-121458 · Severity: medium · CVSS 6.5 · Published 2026-11-03

Instatic is a content management system that allows users to manage and publish content. An authorization flaw in its AI/MCP (Model Context Protocol) interface allows low-privileged users to read other users' private draft content and enumerate system data that they should not have access to. An attacker with basic editing permissions can bypass security checks and steal sensitive unpublished content from other users.

Technologies: [CoreBunch Instatic](https://junglewise.ai/threats/technologies/instatic). Vendors: [CoreBunch](https://junglewise.ai/threats/vendors/corebunch).

## Quick answers

**Is CVE-2026-121458 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-121458 being exploited in the wild.

**How severe is CVE-2026-121458?** Medium severity, with a CVSS score of 6.5, published 3 November 2026.

**Which products and versions are affected?** CoreBunch Instatic before 0.0.21.

**Is there a fix for CVE-2026-121458?** Yes: fixed in 0.0.21. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is CVE-2026-121458 attacked?** It is attacked over the network.

**Am I affected by CVE-2026-121458?** Check whether you run CoreBunch Instatic at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- Fixed in 0.0.21

## Technical details

The AI/MCP content read tools (content_get_document, content_list_documents, content_search_documents) fail to enforce object-level authorization checks that are correctly enforced by the normal HTTP API. An authenticated user with ai.chat and content.edit.own capabilities can call these tools via the MCP endpoint to retrieve rows belonging to other users. The HTTP endpoint correctly returns 404 for unauthorized access, proving the authorization boundary exists but is not enforced on the MCP tool surface.

## Affected products

- CoreBunch Instatic before 0.0.21

## Timeline

- 2026-11-03: disclosed
- 2026-10-12: patched: v0.0.21 released on GitHub

## References

- [https://github.com/CoreBunch/Instatic/releases/tag/v0.0.21](https://github.com/CoreBunch/Instatic/releases/tag/v0.0.21)
- [https://github.com/CoreBunch/Instatic/security/advisories/GHSA-x5cc-8486-8qqx](https://github.com/CoreBunch/Instatic/security/advisories/GHSA-x5cc-8486-8qqx)

## Related threats

- [Instatic authorization bypass in handleRowAuthor](https://junglewise.ai/threats/cve-2026-125398-instatic-before-0-0-21-contains-an-authorization-bypass)
- [CoreBunch Instatic cache poisoning in render endpoint](https://junglewise.ai/threats/cve-2026-72587-corebunch-instatic-cache-poisoning-in-render-endpoint)