CVE-2026-13063 Overview
CVE-2026-13063 is a denial-of-service vulnerability in MongoDB affecting the libmongocrypt library. An authenticated user holding standard read/write privileges can terminate the mongod process by submitting a crafted aggregation command. The library performs insufficient validation on payload-supplied values, leading to an excessively large memory allocation and an out-of-memory condition. The weakness is categorized under [CWE-190] (Integer Overflow or Wraparound). The flaw requires low privileges and no user interaction, and it is exploitable over the network against the database service.
Critical Impact
Any authenticated MongoDB user with standard read/write privileges can crash the mongod process through a single crafted aggregation command, disrupting database availability.
Affected Products
- MongoDB Server (mongod) instances using the libmongocrypt library
- MongoDB deployments accepting aggregation commands from authenticated users
- Client-Side Field Level Encryption workflows relying on libmongocrypt
Discovery Timeline
- 2026-07-22 - CVE-2026-13063 published to NVD
- 2026-07-22 - Last updated in NVD database
Technical Details for CVE-2026-13063
Vulnerability Analysis
The vulnerability resides in MongoDB's libmongocrypt library, which handles cryptographic operations for client-side field level encryption. The library accepts payload-supplied values during aggregation command processing without adequately validating their size. When an authenticated attacker submits a crafted aggregation command containing manipulated length or size fields, libmongocrypt attempts to allocate memory proportional to the attacker-controlled value. The resulting allocation request exceeds available memory, causing the mongod process to terminate.
Because the crash occurs at the process level, all connected clients lose their sessions and pending operations fail. In replicated deployments, repeated exploitation forces failovers and degrades cluster stability.
Root Cause
The root cause is insufficient input validation on payload-supplied numeric values inside libmongocrypt. The library trusts size fields carried in the aggregation payload and forwards them into allocation routines without bounding them against realistic maximums or available memory. This aligns with the [CWE-190] classification, where an oversized or overflowed integer drives a downstream allocation.
Attack Vector
Exploitation requires network access to the MongoDB service and valid credentials with standard read/write privileges. No elevated role, no user interaction, and no local access are required. The attacker connects to mongod, authenticates, and issues an aggregation command whose encryption-related payload contains a crafted size value. The server-side libmongocrypt processing attempts the oversized allocation and the mongod process terminates.
The vulnerability affects availability only. Confidentiality and integrity are not directly impacted, according to the CVSS vector. Technical details are tracked in the MongoDB JIRA Issue SERVER-127737.
Detection Methods for CVE-2026-13063
Indicators of Compromise
- Unexpected mongod process terminations with out-of-memory errors logged by the OS or container runtime
- MongoDB server logs showing abrupt session terminations following aggregation commands from authenticated users
- Repeated crashes correlated with the same authenticated principal or source IP submitting aggregation pipelines
Detection Strategies
- Monitor mongod server logs for aggregation commands issued immediately before process termination or restart events
- Alert on kernel oom-killer events targeting mongod on database hosts
- Track authenticated sessions that trigger repeated abnormal disconnects during aggregation workloads
Monitoring Recommendations
- Ingest MongoDB audit logs and host telemetry into a centralized analytics platform to correlate crashes with client identities and command payloads
- Track memory utilization on database hosts and alert on sudden spikes that precede process termination
- Review privileged authentication activity against MongoDB and flag accounts issuing anomalous aggregation pipelines
How to Mitigate CVE-2026-13063
Immediate Actions Required
- Apply the MongoDB update that addresses the libmongocrypt validation issue tracked in SERVER-127737 once available for your release channel
- Audit database roles and remove read/write privileges from accounts that do not require them
- Restrict network reachability of mongod to trusted application tiers and administrative networks
Patch Information
Refer to the MongoDB JIRA Issue SERVER-127737 for fix status, affected versions, and release notes. Apply the fixed MongoDB Server build and update libmongocrypt to the corresponding patched version on all client and server components that link the library.
Workarounds
- Limit aggregation privileges to service accounts that require them and remove excess readWrite grants from human or shared accounts
- Deploy mongod behind network segmentation and enforce mutual TLS to reduce the exposed authentication surface
- Configure process supervision to restart mongod automatically and set memory cgroup limits to contain out-of-memory impact on shared hosts
# Configuration example
# Review roles granted on a MongoDB deployment and prune unnecessary readWrite grants
mongosh --eval 'db.getSiblingDB("admin").system.users.find({}, {user:1, roles:1}).pretty()'
# Revoke readWrite from an account that does not require it
mongosh --eval 'db.getSiblingDB("admin").revokeRolesFromUser("reporting_user", [{ role: "readWrite", db: "appdata" }])'
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
