# CVE-2026-81528: NoSQL injection via array replacement bypassing update shape validation in driver write path

> Attackers can inject NoSQL commands via untrusted input in document replacement operations, leading to unauthorized database access or modification.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 27 Aug 2026
- **Updated:** 28 Aug 2026
- **Also known as:** GHSA-3jfm-hm2c-wrqh

## What is CVE-2026-81528?

CVE-2026-81528 is a medium-severity SQL injection vulnerability in MongoDB C# Driver, published on 27 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A MongoDB C# driver document-replacement code path omits the element-name/shape validation that the equivalent write paths apply, so a value supplied as a replacement is forwarded to the server without neutralization of query-language special elements. An application that passes untrusted, loosely-typed input as a replacement value therefore allows that input to be interpreted by the database as update logic rather than as data, executing under the application's own database credentials. Applications using strongly-typed document mappings are not affected.

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

## Which versions are affected by CVE-2026-81528?

It affects 1 product.


Products: Mongodb C\# Driver.

## How do I fix CVE-2026-81528?

No fix has been published for CVE-2026-81528 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-81528 being exploited?

There is no known exploitation of CVE-2026-81528 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-2026-81527](https://insights.sbomify.com/CVE-2026-81527/): NoSQL injection via unquoted constant GroupBy keys in LINQ pipeline translation (medium 6.9)
- [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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-81528 and fix it if it is affected.

What it is: CVE-2026-81528 is a medium-severity SQL injection vulnerability in MongoDB C# Driver, published on 27 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-81528 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-2026-81528/ (Markdown: https://insights.sbomify.com/CVE-2026-81528/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81528
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81528
- OSV: https://osv.dev/vulnerability/CVE-2026-81528

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-81528/
Summaries are generated and may contain mistakes; the official description above is the record.