CVE-2026-9741: Client side encryption fails to encrypt values in a $vectorSearch

Synopsis

This is an encryption bypass bug in MongoDB Server affecting the $vectorSearch aggregation stage when Queryable Encryption (QE) or Client-Side Field Level Encryption (CSFLE) is configured. An authenticated attacker with a low-privilege account can send queries that cause literal values in $vectorSearch filter expressions to reach the server as plaintext instead of being encrypted, bypassing the confidentiality guarantees those features are designed to provide. Successful exploitation exposes sensitive field values that were intended to remain encrypted in transit to the server. Patched-image rebuilds at versions 7.0.35, 8.0.24, 8.2.10, and 8.3.3 are available on HarborGuard for affected environments.

HarborGuard Coverage

Exploit Conditions

• Network reachabilityRequired

  The attacker must be able to reach the MongoDB service over the network to submit queries against it.

• AuthenticationRequired

  A low-privilege account is sufficient; the attacker must be authenticated to the MongoDB instance to issue $vectorSearch aggregation queries.

• Victim interactionNot required

  No user interaction is needed; the attacker submits a malformed query directly and the server processes it without any other party taking action.

• Attack complexityDetail

  Exploit conditions are straightforward and reliable with no race conditions or special environmental configuration required.

Blast Radius

• The attacker reads plaintext values of fields that were meant to be protected by Queryable Encryption or Client-Side Field Level Encryption, including any sensitive data stored in those fields such as personal identifiers, credentials, or application-specific secrets.
• Confidentiality of encrypted field values in $vectorSearch filter expressions is fully compromised for any query the attacker can submit.
• No data integrity or availability impact is present; the database contents are not modified and the service remains operational.