# CVE-2026-106436: Application denial of service and data truncation via unchecked BSON append failures in MongoDB PHP Driver

> An unauthenticated attacker can cause denial of service or data truncation in applications using the MongoDB PHP Driver by triggering unchecked BSON append failures.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/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:** Yes
- **Published:** 8 Oct 2026
- **Updated:** 8 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-106436, UBUNTU-CVE-2026-106436

## What is CVE-2026-106436?

CVE-2026-106436 is a medium-severity denial of service vulnerability in MongoDB PHP Driver, published on 8 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The BSON encoder in the MongoDB PHP Driver does not check some return values after a document exceeds libbson's size limit. This can leave the encoder in an invalid state. An unauthenticated actor who can cause an affected application to encode an unusually large data structure can terminate the PHP worker or cause the resulting document to omit fields. No MongoDB server connection or database authentication is required.

Weakness: CWE-252 (Unchecked Return Value)

## Which versions are affected by CVE-2026-106436?

It affects 1 product.


Products: Mongodb Php Driver.

## How do I fix CVE-2026-106436?

Upgrade to a fixed version.

## Is CVE-2026-106436 being exploited?

There is no known exploitation of CVE-2026-106436 in the wild and no public exploit code.

## Other vulnerabilities in MongoDB PHP Driver

- [CVE-2026-81525](https://insights.sbomify.com/CVE-2026-81525/): Cross-tenant database retargeting via dot/NUL injection in namespace strings in the PHP Driver (high 8.6)
- [CVE-2026-84968](https://insights.sbomify.com/CVE-2026-84968/): Heap out-of-bounds read via corrupt nested BSON in field path error message (medium 6.9)
- [CVE-2026-6811](https://insights.sbomify.com/CVE-2026-6811/): PHP Stack Exhaustion (medium 6.0)
- [CVE-2026-106432](https://insights.sbomify.com/CVE-2026-106432/): Heap buffer overflow via 32-bit string-length truncation in MongoDB PHP Driver (low 2.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-106436 and fix it if it is affected.

What it is: CVE-2026-106436 is a medium-severity denial of service vulnerability in MongoDB PHP Driver, published on 8 Oct 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-2026-106436 in the wild and no public exploit code.

Affected product: MongoDB PHP 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-2026-106436/ (Markdown: https://insights.sbomify.com/CVE-2026-106436/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-106436
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-106436
- OSV: https://osv.dev/vulnerability/CVE-2026-106436

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-106436/
Summaries are generated and may contain mistakes; the official description above is the record.