CVE-2026-81529Network attack vectorHinoki check available

Connection-option injection via unescaped URL-builder settings

Published Aug 27, 2026 · Updated Aug 27, 2026

Connection-option injection in MongoDB .NET/C# Driver 3.5.0 through 3.11.0 allows attackers to alter connection settings. The canonical URL builder serializes untrusted setting text without neutralizing URL and option delimiters, then reparses the result as authoritative client configuration. Exploitation requires a low-privileged application user to influence builder input and the application to round-trip that builder, enabling security-relevant options to be introduced or suppressed.

CVSS severityUnavailable
Unscored
EPSS probability0.17%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Connection-option injection in MongoDB .NET/C# Driver 3.5.0 through 3.11.0 allows attackers to alter connection settings. The canonical URL builder serializes untrusted setting text without neutralizing URL and option delimiters, then reparses the result as authoritative client configuration. Exploitation requires a low-privileged application user to influence builder input and the application to round-trip that builder, enabling security-relevant options to be introduced or suppressed.

The record

CVE
CVE-2026-81529
Published
Aug 27, 2026
Updated
Aug 27, 2026
Vendor
MongoDB
Product
MongoDB .NET/C# Driver
Classifications
Unavailable
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=3.5.0 <3.11.1

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

MongoDB · MongoDB .NET/C# Driverversion=3.5.0 <3.11.1

Published CVSS scores

No CVSS assessment is available in this record.

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.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

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

No sourced classifications are available.

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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