CVE-2026-81522Network attack vector

Cross-tenant data access via namespace delimiter injection

Published Aug 27, 2026 · Updated Aug 27, 2026

Improper output encoding in MongoDB C++ Driver 3.0.0 through 4.5.0 allows remote authenticated users to read or write cross-tenant data. Database names containing dots and database or collection names containing NUL bytes are silently reinterpreted during namespace encoding instead of rejected. Exploitation requires an application to build namespace identifiers from untrusted input; the resulting operation can target another logical tenant's data.

CVSS severity8.6
High
EPSS probability0.27%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper output encoding in MongoDB C++ Driver 3.0.0 through 4.5.0 allows remote authenticated users to read or write cross-tenant data. Database names containing dots and database or collection names containing NUL bytes are silently reinterpreted during namespace encoding instead of rejected. Exploitation requires an application to build namespace identifiers from untrusted input; the resulting operation can target another logical tenant's data.

The record

CVE
CVE-2026-81522
Published
Aug 27, 2026
Updated
Aug 27, 2026
Vendor
MongoDB
Product
MongoDB .NET/C# Driver
Classifications
CWE-116
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Aug 27, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 27, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=3.0.0 <4.5.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

MongoDB · MongoDB .NET/C# Driverversion=3.0.0 <4.5.1

Published CVSS scores

8.6MongoDB CNACVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N
8.1MongoDB CNACVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-116Improper Encoding or Escaping of Output

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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