# CVE-2026-118581: NoSQL injection via mismatched BSON size prefix in raw document splice to the wire protocol


- **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
- **Fix available:** No
- **Published:** 28 Oct 2026
- **Updated:** 28 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-118581

## What is CVE-2026-118581?

CVE-2026-118581 is a medium-severity vulnerability in MongoDB Java Driver, published on 28 Oct 2026. 

### Official description

A BSON encoding component of the MongoDB Java Driver does not verify that an externally supplied raw document's self-declared length agrees with the extent of the byte range it is given before that range is copied into an outgoing database command. An application that wraps untrusted raw bytes in such a document and uses it as part of a command can therefore emit a structurally inconsistent message, causing the database to interpret attacker-supplied trailing content as additional fields of the surrounding command. No authentication to the driver or database is required beyond the ability to influence those bytes through the victim application, and no user interaction is needed. The result is unintended modification of the command actually executed, which can alter the data read or written under the application's credentials.

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

## Which versions are affected by CVE-2026-118581?


## How do I fix CVE-2026-118581?

No fix has been published for CVE-2026-118581 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-118581 being exploited?

There is no known exploitation of CVE-2026-118581 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-118581 and fix it if it is affected.

What it is: CVE-2026-118581 is a medium-severity vulnerability in MongoDB Java Driver, published on 28 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-118581 in the wild and no public exploit code.

Affected product: MongoDB Java 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-2026-118581/ (Markdown: https://insights.sbomify.com/CVE-2026-118581/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-118581
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-118581
- OSV: https://osv.dev/vulnerability/CVE-2026-118581

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-118581/
Summaries are generated and may contain mistakes; the official description above is the record.