Description

Craft CMS versions before 5.10.11 contain a site scope bypass vulnerability in GraphQL entry mutation resolvers that fail to validate siteId through ArgumentManager::prepareArguments(). Attackers with tokens scoped to one site can read, modify, or delete entries across unauthorized sites by passing siteId directly in mutation arguments.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-09-02T12:17:16.227Z",
  "pubdate": "2026-09-02T12:17:16.227Z",
  "executiveSummary": "Craft CMS versions prior to 5.10.11 are susceptible to a site scope bypass vulnerability within their GraphQL entry mutation resolvers.\nThe vulnerability arises from insufficient input validation during the processing of GraphQL mutation arguments, specifically regarding the 'siteId' parameter.\nAn authenticated attacker possessing a token scoped to a single, legitimate site can escalate their privileges to perform unauthorized read, modification, or deletion operations on entries across other sites within the same Craft CMS installation.\nThis vulnerability highlights a critical failure in the enforcement of multi-site access control policies at the API layer.\nThe risk implication is significant, as it permits unauthorized cross-site data manipulation and exfiltration, potentially compromising the integrity and confidentiality of the entire multi-site environment.\nExploitation requires an existing, valid authentication token, though the scope of that token is effectively ignored by the vulnerable mutation resolvers, allowing the attacker to bypass organizational boundaries defined by the CMS's multi-site architecture.",
  "technicalDetails": "The vulnerability originates in the GraphQL entry mutation resolvers within Craft CMS, which fail to properly sanitize or validate the 'siteId' argument passed via the ArgumentManager::prepareArguments() method.\nIn a multi-site Craft CMS installation, the system is designed to isolate content based on specific site IDs to ensure that users or API clients can only interact with entries belonging to their authorized scope.\nThe 'ArgumentManager::prepareArguments()' function, intended to sanitize and validate incoming mutation parameters, does not enforce the 'siteId' restriction when processing requests for entry mutations.\nAn attacker can exploit this by crafting a GraphQL mutation request (e.g., saveEntry, deleteEntry) and explicitly including a 'siteId' parameter corresponding to a site for which their current authentication token does not grant permission.\nBecause the resolver trusts the provided 'siteId' without reconciling it against the authenticated user's assigned permissions or the token's scope, the application proceeds to execute the requested operation on the unauthorized target site.\nThe attack flow begins with the attacker obtaining a valid authentication token scoped to at least one authorized site. They then interact with the GraphQL endpoint, submitting a mutation query that targets an entry ID or attempts to create an entry while overriding the 'siteId' argument.\nThe backend service processes the mutation, bypassing internal security checks that should prevent cross-site activity. Consequently, the mutation is executed against the attacker-specified site, resulting in unauthorized data modification, content injection, or record deletion.\nThis vulnerability affects Craft CMS versions prior to 5.10.11. The failure effectively renders the multi-site isolation features useless against an attacker with any form of authenticated access, as the input validation logic is bypassed entirely during the GraphQL resolution phase.\nThe impact post-exploitation is substantial: an attacker could manipulate content across all sites in the installation, leading to unauthorized data exposure, defacement, or the corruption of business-critical information across the entire CMS infrastructure."
}