Authorization Bypass in Instatic AI/MCP Content Read Tools Affects Data Security
CVE-2026-121458

7.1HIGH

Key Information:

Vendor

Corebunch

Status
Instatic
Vendor
CVE Published:
3 November 2026

What is CVE-2026-121458?

Instatic versions prior to 0.0.21 are vulnerable to an authorization bypass that allows low-privileged authenticated users, specifically those with ai.chat and content.edit.own capabilities, to access restricted data. This occurs through the use of content_read_document and content_list_documents functions without the necessary object-level authorization checks typical of HTTP API interactions. Consequently, attackers can retrieve private or unpublished draft content and enumerate entries from the posts system table, leading to potential cross-user data exposure.

Affected Version(s)

Instatic 0.0.12 < 0.0.21

References

https://github.com/CoreBunch/Instatic/security/advisories...
vendor-advisorytechnical-description
https://github.com/CoreBunch/Instatic/releases/tag/v0.0.21
patchissue-tracking
https://www.vulncheck.com/advisories/instatic-before-auth...
third-party-advisory

CVSS V4

Score:
7.1
Severity:
HIGH
Confidentiality:
High
Integrity:
None
Availability:
None
Attack Vector:
Network
Attack Complexity:
Low
Attack Required:
None
Privileges Required:
Undefined
User Interaction:
None

Timeline

  • Vulnerability published

  • Vulnerability Reserved

Credit

Sriman Aluvala
.