# CVE-2026-81529 — MongoDB C# Driver

> As of 2026-08-28, CVE-2026-81529 is a HIGH-severity vulnerability in MongoDB C# Driver, CVSS v3.1 7.1, EPSS 0.1% (6.9th percentile). No Threadlinqs-tracked threat campaign has been attributed to CVE-2026-81529 as of 2026-08-28; the identifier is re-checked against the Threadlinqs threat corpus on every daily ingest.

**Last updated:** 2026-08-28

## What is CVE-2026-81529?

Improper neutralization of delimiters in connection-URL construction allows connection-option injection in the MongoDB C# Driver. When an application passes untrusted text into the driver's connection-URL builder and round-trips the builder back into a client configuration, the untrusted text is serialized without neutralizing the URL/option delimiters and is then re-parsed as authoritative connection options. A low-privileged user of such an application can thereby introduce or suppress security-relevant connection settings.

The record classifies CVE-2026-81529 under weakness class [CWE-88](https://intel.threadlinqs.com/cwe/CWE-88). Its CVSS v3 base vector states that the flaw is reachable remotely over the network, needs low-privilege credentials, needs no user interaction, and has high impact on confidentiality. 1 affected-product entry is recorded, across 1 vendor, listed below. The identifier was first published 39 days ago.

## Severity and exploitation probability

- **CVSS v3.1 base score:** 7.1 — HIGH (`CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N`)
- **CVSS v4.0 base score:** 7.1 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:H/VI:L/VA:N/SC:H/SI:L/SA:N`)
- **EPSS (FIRST):** 0.1% probability of exploitation in the next 30 days, higher than 6.9% of all scored CVEs
- **CISA KEV:** Not listed in the CISA Known Exploited Vulnerabilities catalog
- **Threadlinqs priority:** 3.8/10 — a Threadlinqs composite of the CVSS base score, the EPSS percentile and public exploit availability
- **Published:** 2026-08-27, last modified 2026-08-28

## Is CVE-2026-81529 being exploited?

It currently carries a trending score of 31 in the Threadlinqs vulnerability feed.

## Affected products and versions

- [MongoDB](https://intel.threadlinqs.com/vendors/mongodb): C# Driver

## How to fix CVE-2026-81529

No vendor patch reference has been recorded for CVE-2026-81529 in the tracked sources. Follow the references below for a fix, and treat the products listed above as exposed until the vendor states otherwise.

## Threat activity tracking CVE-2026-81529

No threat campaign in the Threadlinqs corpus currently references CVE-2026-81529, in its CVE list or as an indicator. The linkage is recomputed from the live corpus on every daily ingest, so this section fills in as soon as a tracked campaign cites the identifier.

## Sources

Enriched from CVE.org, NVD, FIRST EPSS. Last verified by Threadlinqs on 2026-08-30. This product uses the NVD API but is not endorsed or certified by the NVD.

**Other references**

- [jira.mongodb.org](https://jira.mongodb.org/browse/CSHARP-6171)
- [nuget.org](https://www.nuget.org/packages/MongoDB.Driver/3.11.1)

Canonical: https://intel.threadlinqs.com/cve/CVE-2026-81529
Full detection coverage and IOCs for threats exploiting CVE-2026-81529 via the Threadlinqs MCP server (Purple tier): https://intel.threadlinqs.com/mcp