# CVE-2026-84968: Heap out-of-bounds read via corrupt nested BSON in field path error message

> An attacker can trigger an out-of-bounds read in the MongoDB PHP driver to disclose limited process memory contents via error messages.

- **Severity:** Medium 6.9 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/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:** 3 Sep 2026
- **Updated:** 4 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-84968, UBUNTU-CVE-2026-84968

## What is CVE-2026-84968?

CVE-2026-84968 is a medium-severity vulnerability in MongoDB PHP Driver, published on 3 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An out-of-bounds read in the BSON decoding component of the MongoDB PHP driver may allow an unauthenticated party who supplies specially formed input to have a small amount of adjacent process memory copied into an error message that is returned to application code. This may result in unintended disclosure of limited memory contents.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-84968?

It affects 1 product.


Products: Mongodb Php Driver.

## How do I fix CVE-2026-84968?

Upgrade to a fixed version.

## Is CVE-2026-84968 being exploited?

There is no known exploitation of CVE-2026-84968 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-2026-106436](https://insights.sbomify.com/CVE-2026-106436/): Application denial of service and data truncation via unchecked BSON append failures in MongoDB PHP Driver (medium 6.3)
- [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-2026-84968 and fix it if it is affected.

What it is: CVE-2026-84968 is a medium-severity vulnerability in MongoDB PHP Driver, published on 3 Sep 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-2026-84968 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-2026-84968/ (Markdown: https://insights.sbomify.com/CVE-2026-84968/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-84968
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-84968
- OSV: https://osv.dev/vulnerability/CVE-2026-84968

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-84968/
Summaries are generated and may contain mistakes; the official description above is the record.