# CVE-2026-106433: Heap corruption via duplicate masterKey fields in MongoDB libmongocrypt

> An authenticated attacker can cause heap corruption and potential code execution in MongoDB libmongocrypt by manipulating key vault documents with duplicate masterKey fields.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:H/VA:H/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:** Yes
- **Published:** 8 Oct 2026
- **Updated:** 8 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-106433, UBUNTU-CVE-2026-106433

## What is CVE-2026-106433?

CVE-2026-106433 is a high-severity memory corruption vulnerability in MongoDB libmongocrypt, published on 8 Oct 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Improper state management in MongoDB libmongocrypt can cause provider-specific data to be treated as an incompatible type when cleaning up a key document containing duplicate masterKey fields. An authenticated actor who can modify key vault documents, or a server that returns such a key document, can cause invalid memory access and invalid frees in the client process. This can terminate the application or corrupt process memory.

Weakness: CWE-843 (Access of Resource Using Incompatible Type)

## Which versions are affected by CVE-2026-106433?

It affects 1 product.


Products: Mongodb Libmongocrypt.

## How do I fix CVE-2026-106433?

Upgrade to a fixed version.

## Is CVE-2026-106433 being exploited?

There is no known exploitation of CVE-2026-106433 in the wild and no public exploit code.

## Other vulnerabilities in MongoDB libmongocrypt

- [CVE-2026-84971](https://insights.sbomify.com/CVE-2026-84971/): Persistent client crash loop via undersized FLE2 insert-update ciphertext in decryption path (high 7.1)
- [CVE-2026-84962](https://insights.sbomify.com/CVE-2026-84962/): Authenticated KMS request forgery via CRLF injection in GCP key identifier strings (medium 5.7)
- [CVE-2026-81523](https://insights.sbomify.com/CVE-2026-81523/): Cross-tenant database retargeting via dot/NUL injection in namespace strings in libmongocrypt (low 2.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-106433 and fix it if it is affected.

What it is: CVE-2026-106433 is a high-severity memory corruption vulnerability in MongoDB libmongocrypt, published on 8 Oct 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-2026-106433 in the wild and no public exploit code.

Affected product: MongoDB libmongocrypt. 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-2026-106433/ (Markdown: https://insights.sbomify.com/CVE-2026-106433/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-106433
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-106433
- OSV: https://osv.dev/vulnerability/CVE-2026-106433

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-106433/
Summaries are generated and may contain mistakes; the official description above is the record.