CVE-2026-18699 Overview
CVE-2026-18699 is a denial-of-service vulnerability in MongoDB Server's query planner. An authenticated user holding only read-level privileges can crash the mongod process by submitting a specially crafted query against a collection that has a text index. The failure originates in a null pointer dereference [CWE-476] triggered during query planning.
When the server process terminates, all connected clients are disconnected and in-flight operations are aborted. Repeated exploitation can be used to keep a database node offline, disrupting application availability.
Critical Impact
Any authenticated account with read permissions on a collection that carries a text index can crash the MongoDB server on demand, producing a persistent denial-of-service condition against database clients.
Affected Products
- MongoDB Server deployments that expose collections with a text index
- Environments where read-level database users can issue arbitrary find or aggregation queries
- Deployments tracked under the vendor issue MongoDB SERVER-130266
Discovery Timeline
- 2026-08-11 - CVE-2026-18699 published to the National Vulnerability Database
- 2026-08-11 - Last updated in the NVD database
Technical Details for CVE-2026-18699
Vulnerability Analysis
The defect lives in MongoDB Server's query planner. The planner selects execution strategies based on available indexes, including text indexes used for full-text search. A specially formed query against a collection with a text index causes the planner to dereference a null pointer, terminating the mongod process.
Exploitation requires authentication and read-level privileges on the target collection. No write access, administrative role, or user interaction is needed. The attack is network-reachable through the standard MongoDB wire protocol. Confidentiality and integrity are not directly affected; the impact is limited to availability of the database node.
The underlying weakness is classified as a null pointer dereference [CWE-476]. See the vendor tracker at MongoDB SERVER-130266 for issue details.
Root Cause
The query planner fails to validate an internal pointer before dereferencing it while processing certain query shapes that combine text index predicates with specific operator patterns. The missing check turns a malformed but authenticated request into an unhandled fault that terminates the process.
Attack Vector
An authenticated attacker connects to the MongoDB instance over the network and issues a crafted query targeting a collection with a text index. The planner processes the query, hits the null dereference, and the mongod process exits. Verified proof-of-concept code is not publicly available; refer to the linked MongoDB issue tracker entry for reproduction details.
Detection Methods for CVE-2026-18699
Indicators of Compromise
- Unexpected mongod process terminations correlated with client query activity rather than resource exhaustion or operator action
- Server logs showing planner-related fatal signals or stack traces referencing text index code paths
- Bursts of client disconnects and driver reconnection storms following a single query from one authenticated session
Detection Strategies
- Monitor MongoDB server logs for abnormal shutdown messages, SIGSEGV events, and crash dumps generated by mongod
- Correlate query audit records with server restarts to identify the specific authenticated user and query shape that preceded a crash
- Alert on repeated crash-and-restart cycles on the same replica set member within short time windows
Monitoring Recommendations
- Enable MongoDB auditing to capture the originating user, source IP, and command payload for queries preceding process termination
- Track replica set health metrics and primary step-downs, which will spike if a targeted node repeatedly crashes
- Forward mongod logs and audit events to a centralized analytics platform so query patterns can be reviewed across nodes
How to Mitigate CVE-2026-18699
Immediate Actions Required
- Inventory collections that carry a text index and identify which application roles can query them
- Restrict read privileges on those collections to the minimum set of accounts required for business function
- Review recent audit logs for unexpected query patterns from read-only accounts targeting text-indexed collections
- Prepare change windows to apply the fixed MongoDB Server release once available for your deployment channel
Patch Information
Refer to the vendor issue MongoDB SERVER-130266 for the list of fixed versions and upgrade guidance. Apply the corresponding patched MongoDB Server release for your deployment channel, including MongoDB Atlas, Enterprise, and Community editions as applicable.
Workarounds
- Remove or temporarily drop non-essential text indexes from collections accessible to lower-privilege users until patching is complete
- Rotate credentials for read-level accounts that are no longer required and revoke unused role bindings
- Place MongoDB endpoints behind network controls that limit connections to trusted application tiers only
- Deploy replica sets with automatic failover so a single crashed node does not translate into full application downtime
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
