# CVE-2026-81527: NoSQL injection via unquoted constant GroupBy keys in LINQ pipeline translation

> Attackers can inject logic into MongoDB queries via unescaped LINQ keys, potentially altering results or exposing unintended data.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Aug 2026
- **Updated:** 28 Aug 2026
- **Also known as:** GHSA-qvhj-5652-cjrg

## What is CVE-2026-81527?

CVE-2026-81527 is a medium-severity SQL injection vulnerability in MongoDB C# Driver, published on 27 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A NoSQL/expression injection weakness exists in the LINQ-to-aggregation query translation layer of the MongoDB C# Driver, in both aggregation expression and query filter translation. When application-supplied values are embedded in certain query constructs, special elements contained within those values are not properly escaped before the resulting query is transmitted to the database, so portions of the value may be interpreted by the database as query logic rather than as data. A user able to supply values that an application incorporates into an affected query may thereby cause unintended data to be returned or query results to be altered.

Weakness: CWE-943 (Improper Neutralization of Special Elements in Data Query Logic)

## Which versions are affected by CVE-2026-81527?

It affects 1 product.


Products: Mongodb C\# Driver.

## How do I fix CVE-2026-81527?

No fix has been published for CVE-2026-81527 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-81527 being exploited?

There is no known exploitation of CVE-2026-81527 in the wild and no public exploit code.

## Other vulnerabilities in MongoDB C# Driver

- [CVE-2026-88026](https://insights.sbomify.com/CVE-2026-88026/): Regular expression injection via unescaped characters in LINQ query translation in MongoDB C# Driver (high 7.1)
- [CVE-2026-81529](https://insights.sbomify.com/CVE-2026-81529/): Connection-option injection via unescaped settings in the canonical MongoDB URL builder (high 7.1)
- [CVE-2026-81530](https://insights.sbomify.com/CVE-2026-81530/): KMS master key exposure via unredacted credential serialization in driver settings string (medium 6.8)
- [CVE-2022-48282](https://insights.sbomify.com/CVE-2022-48282/): Deserializing compromised object with MongoDB .NET/C# Driver may cause remote code execution (medium 6.6)
- [CVE-2026-88025](https://insights.sbomify.com/CVE-2026-88025/): GridFS data disclosure and deletion via query-operator injection in file IDs in the MongoDB C# Driver (medium 6.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-81527 and fix it if it is affected.

What it is: CVE-2026-81527 is a medium-severity SQL injection vulnerability in MongoDB C# Driver, published on 27 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-81527 in the wild and no public exploit code.

Affected product: MongoDB C# Driver. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-81527/ (Markdown: https://insights.sbomify.com/CVE-2026-81527/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81527
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81527
- OSV: https://osv.dev/vulnerability/CVE-2026-81527

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-81527/
Summaries are generated and may contain mistakes; the official description above is the record.