# CVE-2026-106434: Unrecognized payload acceptance in explicit decryption in MongoDB libmongocrypt

> Attackers can inject unrecognized payloads into encrypted fields, causing applications to process them as plaintext, potentially leading to data exposure or logic errors.

- **Severity:** Medium 5.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:N/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:** Yes
- **Published:** 8 Oct 2026
- **Updated:** 8 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-106434, UBUNTU-CVE-2026-106434

## What is CVE-2026-106434?

CVE-2026-106434 is a medium-severity 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

The explicit decryption component of MongoDB libmongocrypt can return an unrecognized encrypted payload unchanged instead of returning a decryption error. An actor who can modify stored encrypted fields, such as a database writer, server, or network intermediary, can cause an affected application to process the supplied bytes as decrypted plaintext.

Weakness: CWE-354 (Improper Validation of Integrity Check Value)

## Which versions are affected by CVE-2026-106434?


## How do I fix CVE-2026-106434?

Upgrade to a fixed version.

## Is CVE-2026-106434 being exploited?

There is no known exploitation of CVE-2026-106434 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-106434 and fix it if it is affected.

What it is: CVE-2026-106434 is a medium-severity 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-2026-106434 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-2026-106434/ (Markdown: https://insights.sbomify.com/CVE-2026-106434/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-106434
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-106434
- OSV: https://osv.dev/vulnerability/CVE-2026-106434

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-106434/
Summaries are generated and may contain mistakes; the official description above is the record.