Description

An issue in MongoDB Server's handling of timeseries bucket lifecycle could allow an authenticated user with write privileges to cause an internal reference to be used after the underlying memory has been freed. Subsequent operations could then result in a server crash or, potentially, execution of unintended code.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "8.8",
  "pubDate": "2026-08-11T19:17:23.317Z",
  "pubdate": "2026-08-11T19:17:23.317Z",
  "executiveSummary": "A use-after-free vulnerability has been identified in MongoDB Server's handling of timeseries bucket lifecycles. The vulnerability arises within the timeseries bucket management component, where improper memory lifecycle management allows internal references to persist after the underlying memory has been deallocated.\nExploitation of this flaw requires an authenticated user with write privileges against the database. Depending on the specific execution context and memory layout state, a successful exploit can lead to a denial of service via server crash or, theoretically, the execution of unintended native code.\nThe risk implication is severe for environments relying on MongoDB timeseries collections with multi-tenant write access, as malicious or compromised low-privilege service accounts could destabilize the entire database instance.\nMitigation requires applying official vendor patches for the affected MongoDB Server versions once available, adhering to the principle of least privilege regarding database write permissions, and monitoring database error logs for unexpected crashes associated with timeseries operations.",
  "technicalDetails": "The vulnerability is rooted in the memory management logic governing timeseries bucket lifecycles within MongoDB Server. During the insertion and processing of timeseries data, buckets are dynamically allocated, manipulated, and eventually freed in memory. Due to a flaw in how internal references or pointers to these bucket structures are tracked and invalidated, a race condition or logical oversight allows an internal reference to be retained after the underlying memory chunk has been released back to the allocator.\nTo trigger this condition, an authenticated attacker must possess write privileges, allowing them to issue specific sequences of commands or data insertions that interact with the timeseries bucket lifecycle. When the vulnerable component attempts to access the stale internal reference, a use-after-free (UAF) condition is instantiated.\nThe attack flow proceeds as follows: 1. The attacker establishes an authenticated session with write permissions. 2. The attacker executes operations targeting timeseries collections designed to manipulate bucket allocation and deallocation states. 3. The database engine frees the underlying memory of a timeseries bucket while retaining a dangling pointer internally. 4. Subsequent operations trigger access to the dangling pointer, resulting in undefined behavior.\nIf the freed memory is rapidly reallocated by another thread or process, referencing the stale pointer can corrupt critical application state data. This memory corruption typically manifests as an unhandled segmentation fault or assertion failure, causing an immediate server crash (Denial of Service). In more complex scenarios, if heap layout manipulation can be controlled via sophisticated payload behavior, it may potentially facilitate arbitrary code execution under the security context of the mongod process.\nThe vulnerability involves the timeseries subsystem of MongoDB Server, requiring active authentication and write-level access privileges to initiate the bucket lifecycle sequences. Network exposure depends on the database deployment configuration, though internal network access is typically required."
}