Description

An issue in MongoDB Server could allow an authenticated user with direct network access to a shard to improperly commit or abort an in-progress prepared transaction, bypassing the intended transaction coordination process. This could result in cross-shard data inconsistency, cluster clock corruption, and violation of transaction atomicity guarantees.

Executive Summary

Technical Details

Mitigations

References

Additional Metadata

{
  "score": "6.4",
  "pubDate": "2026-08-11T19:17:25.827Z",
  "pubdate": "2026-08-11T19:17:25.827Z",
  "executiveSummary": "An authorization and state-management vulnerability exists within MongoDB Server that permits unauthorized state transitions in distributed transactions.\nThe flaw allows an authenticated adversary to improperly commit or abort in-progress prepared transactions, entirely bypassing the intended multi-version concurrency control and transaction coordination mechanisms managed by the distributed cluster.\nThe primary impact of successful exploitation includes severe cross-shard data inconsistency, cluster-wide logical clock corruption, and a fundamental violation of ACID atomicity guarantees across distributed database collections.\nThe affected system is MongoDB Server, specifically impacting distributed deployments utilizing sharded clusters.\nThe risk implications are critical for environments relying on strict transactional integrity, as data corruption across shards can silently invalidate application logic and state synchronization.\nTo execute this attack, an adversary must meet specific exploitation requirements: they must possess valid authentication credentials and have direct network access to a target shard within the cluster topology.",
  "technicalDetails": "The vulnerability resides within the transaction coordination component of MongoDB Server, specifically handling the two-phase commit protocol for distributed transactions across sharded architectures.\nThe root cause stems from insufficient validation checks and access control enforcement during the lifecycle management of in-progress prepared transactions on individual shards.\nUnder normal operating conditions, only the designated transaction coordinator can issue commit or abort decisions for a distributed prepared transaction after polling all participating shards.\nHowever, due to inadequate state-machine enforcement and validation at the shard boundary, an authenticated actor with direct network access can directly interact with shard-level transaction primitives.\nThe attack flow proceeds as follows: First, the adversary establishes an authenticated session and identifies an active, in-progress prepared transaction distributed across the cluster. Second, leveraging direct network access to a participating shard, the attacker bypasses the primary transaction coordinator entirely. Third, the attacker issues direct commands to prematurely commit or abort the shard-local branch of the prepared transaction.\nBecause the centralized coordinator is circumvented, the global consensus mechanism becomes desynchronized from the actual state of the shard data.\nThis payload behavior results in fragmented transaction outcomes where one shard commits its local changes while another aborts or remains in a conflicting state.\nThe post-exploitation impact includes persistent cross-shard data anomalies, corruption of cluster logical clocks used for causal consistency, and unrecoverable violation of transaction atomicity, necessitating manual database intervention and data reconciliation."
}