Description

An issue in MongoDB Server's $graphLookup aggregation stage could allow an authenticated user able to issue aggregation and memory-management commands to cause an internal reference to be used after the underlying memory has been freed. This could result in a server crash or, potentially, execution of unintended code.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.6",
  "pubDate": "2026-08-11T19:17:25.360Z",
  "pubdate": "2026-08-11T19:17:25.360Z",
  "executiveSummary": "A use-after-free vulnerability exists in the MongoDB Server $graphLookup aggregation stage. The flaw allows an authenticated user with permissions to issue aggregation and memory-management commands to trigger a memory corruption condition.\nThe primary impact of this vulnerability is a denial of service via server crash, with a potential risk of arbitrary code execution depending on memory layout and exploitation sophistication.\nThe affected product is MongoDB Server, specifically involving the execution handling of the $graphLookup aggregation stage.\nRisk implications are significant for multi-tenant or loosely secured clusters where users possess the necessary baseline database authentication and command execution capabilities.\nAttacker capabilities require authenticated access to the database and the specific ability to issue aggregation queries alongside memory-management commands.\nExploitation requirements rely on precise timing and coordination between memory-management operations and the evaluation of the $graphLookup pipeline stage to induce the use-after-free condition.",
  "technicalDetails": "The vulnerability resides within the MongoDB Server component responsible for processing the $graphLookup aggregation stage.\nThe root cause stems from a memory management flaw where an internal reference is improperly tracked or retained after the underlying memory allocation has been deallocated.\nWhen an authenticated user issues a specially crafted combination of aggregation commands utilizing $graphLookup and concurrent memory-management commands, the database engine interacts with the dangling pointer.\nThe attack flow begins with the attacker authenticating to the MongoDB Server with privileges sufficient to run aggregation pipelines and memory-management routines.\nThe attacker initiates the vulnerable $graphLookup execution, prompting the server to allocate and subsequently free the underlying memory while internal data structures retain a reference to the stale memory address.\nSubsequent access to this internal reference results in a use-after-free condition.\nThe payload behavior and post-exploitation impact manifest either as an immediate segmentation fault leading to an abrupt server crash (Denial of Service) or, under theoretical advanced exploitation vectors, the manipulation of heap memory to achieve execution of unintended code.\nThe vulnerability requires authenticated access, specific command execution capabilities, and affects server deployments where users can interact with the $graphLookup pipeline stage and memory-management subsystems."
}