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CVE-2026-13062 is a confused deputy vulnerability in MongoDB’s Queryable Encryption feature that allows an authenticated user with write privileges on an encrypted collection to modify internal encryption metadata fields through the mongos router in a sharded cluster.
The vulnerability arises from insufficient validation in the mongos router component, which acts as an intermediary between clients and shard servers. In a sharded MongoDB deployment, the mongos router is responsible for routing client requests to the appropriate shard servers. When Queryable Encryption is enabled on a collection, the system maintains internal encryption metadata fields that govern how encrypted data is processed for query operations. These fields are designed to be strictly server-controlled and should never be directly modifiable by clients.
However, the flaw in the validation mechanisms fails to properly distinguish between user-accessible document fields and internally managed encryption metadata components. An attacker with write permissions on a Queryable Encryption-enabled collection can craft specialized write commands that, when routed through mongos, bypass the intended access controls and inject or modify these internal metadata fields.
The technical exploitation leverages the distributed nature of sharded clusters. The mongos router, which normally enforces boundaries between user content and system metadata, does not adequately validate internal flags in write commands. This allows the attacker to manipulate fields that should remain under server control, effectively corrupting the encryption state that maintains query correctness.
The corruption can manifest as false positive or negative results during encrypted queries, potentially leading to unauthorized data access, bypass of encryption controls, or complete denial of service for encrypted collection operations. The vulnerability fundamentally undermines the security model of MongoDB’s Queryable Encryption by enabling data corruption that affects the integrity of encrypted query operations.
Affected versions include MongoDB Server 7.0 before 7.0.39, 8.0 before 8.0.28, 8.2.0 before 8.2.12, and 8.3.0 before 8.3.7. The vulnerability has been assigned a CVSS 3.1 base score of 6.5 (Medium) with vector CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N, and a CVSS 4.0 base score of 7.1 (High). The issue is mapped to CWE-441 (Unintentional Proxy or Intermediary / Confused Deputy).
DailyCVE Form:
Platform: MongoDB Server
Version: 7.0-8.3.x
Vulnerability: Metadata write bypass
Severity: Medium (6.5)
date: 2026-07-22
Prediction: Patch by 2026-08-05
(end of form)
What Undercode Say:
Analytics:
- Attack Vector: Network
- Attack Complexity: Low
- Privileges Required: Low
- User Interaction: None
- Integrity Impact: High
- Confidentiality Impact: None
- Availability Impact: None
- Scope: Unchanged
Bash commands and codes related to the blog
Check MongoDB version
mongod --version
Identify affected versions (7.0 < 7.0.39, 8.0 < 8.0.28, 8.2.0 < 8.2.12, 8.3.0 < 8.3.7)
db.version()
Example of a crafted write command that could exploit the flaw
(This is a conceptual example; actual exploitation requires specific knowledge of internal metadata fields)
db.encryptedCollection.insertOne({
"userField": "value",
"__internalEncryptionMetadata": { "manipulated": "data" }
})
Monitor write operations on encrypted collections
db.setProfilingLevel(2)
db.system.profile.find({ op: "insert" }).pretty()
Check for suspicious write patterns on sharded clusters
db.getSiblingDB("admin").runCommand({ getLog: "global" })
Exploit:
An authenticated user with write privileges on a Queryable Encryption-enabled collection crafts a write command containing malicious modifications to internal encryption metadata fields. The command is sent through the mongos router on a sharded cluster. Due to improper validation of internal flags, the mongos router does not reject the command and forwards it to the shard servers, where the metadata is modified. This corrupts the encryption state and compromises query correctness for encrypted collections.
Protection:
- Upgrade MongoDB Server to patched versions: 7.0.39, 8.0.28, 8.2.12, or 8.3.7 or later.
- Restrict write privileges on Queryable Encryption-enabled collections to only the most trusted users.
- Implement strict role-based access controls (RBAC) and enforce the principle of least privilege.
- Monitor all write commands targeting encryption metadata fields on sharded clusters.
- Enable comprehensive audit logging for all write operations on encrypted collections.
- Implement network segmentation and additional monitoring controls to detect anomalous write patterns.
Impact:
Corruption of encrypted query correctness, potentially leading to false positive or negative results during encrypted queries, unauthorized data access, bypass of encryption controls, and denial of service for encrypted collection operations. The vulnerability compromises the integrity guarantees provided by MongoDB’s Queryable Encryption mechanism.
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Sources:
Reported By: nvd.nist.gov
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