Description

An issue in MongoDB Server's aggregation framework could allow an authenticated user with only read privileges to perform write operations against collections they should not be able to modify. This is due to an internal-use aggregation stage being reachable by external clients without an appropriate authorization check on its embedded operations.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.5",
  "pubDate": "2026-08-11T19:17:25.050Z",
  "pubdate": "2026-08-11T19:17:25.050Z",
  "executiveSummary": "An authorization bypass vulnerability exists within the MongoDB Server aggregation framework, specifically affecting database collections and access control enforcement. This security flaw enables an authenticated user possessing only read-level privileges to successfully execute unauthorized write operations against protected collections that should otherwise restrict such modifications.\nThe risk implications are significant, as low-privileged users can escalate their data manipulation capabilities, leading to potential data integrity violations, unauthorized data insertion, modification, or deletion across sensitive system or application collections.\nThe attacker capabilities require valid authentication to the MongoDB Server instance, but are bounded by a minimal requirement of read privileges rather than write access. Exploitation is achieved by leveraging an internal-use aggregation stage that incorrectly remains reachable by external clients.\nBecause the vulnerable component fails to enforce appropriate authorization checks on its embedded operations, external clients can interface with internal pipeline mechanics designed exclusively for trusted server-side execution. Remediation requires applying official vendor patches or updates to correct the authorization logic within the aggregation subsystem.",
  "technicalDetails": "The root cause of this vulnerability stems from an insufficient authorization check within the MongoDB Server aggregation framework. Specifically, an internal-use aggregation stage is improperly exposed and made directly reachable by external client connections.\nUnder normal operating conditions, MongoDB's role-based access control (RBAC) model strictly segregates read and write operations, ensuring that users provisioned solely with read privileges cannot execute data-modifying commands such as insert, update, or delete.\nHowever, the vulnerability permits an authenticated user to construct and submit a specifically crafted aggregation pipeline containing the exposed internal-use stage. When processed by the server, the pipeline embeds operations that bypass standard privilege validation checks because the internal stage assumes trusted execution context.\nThe attack flow proceeds as follows: First, the authenticated low-privileged user establishes a connection to the MongoDB Server instance. Second, the user crafts an aggregation query utilizing the vulnerable internal-use aggregation stage, embedding unauthorized write or modification instructions within the stage parameters. Third, the client transmits the payload to the server. Fourth, the aggregation subsystem parses the pipeline and executes the embedded operations against target collections without verifying whether the initiating user possesses the requisite write privileges.\nThe affected component is the MongoDB Server aggregation processing engine, specifically the routing and authorization validation logic governing internal aggregation stages. The privilege requirement is authenticated access with read-only permissions, and the network exposure is co-extensive with the database service port. Post-exploitation impact includes unauthorized data tampering, state alteration, and potential integrity compromise of restricted database collections."
}