# CVE-2026-93393: Heap overflow via oversized decrypted TLS record sequence in Windows Secure Channel stream

> A remote attacker can trigger a heap overflow in the MongoDB C Driver's Windows TLS backend, potentially leading to code execution or information disclosure.

- **Severity:** Critical 9.2 (`CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/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:** 17 Sep 2026
- **Updated:** 18 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-93393, GHSA-x65h-hw7w-mq6w, UBUNTU-CVE-2026-93393

## What is CVE-2026-93393?

CVE-2026-93393 is a critical memory corruption vulnerability in MongoDB Inc. C Driver, published on 17 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A heap-based buffer overflow exists in the TLS transport layer of the MongoDB C Driver when built with the Windows platform TLS backend. A remote endpoint that the client connects to can cause the driver to write uncontrolled data outside the bounds of a heap allocation while processing incoming encrypted traffic after the TLS handshake completes. No authentication or user interaction is required, because the affected processing occurs before any application-level authentication completes. Triggering this issue may lead to memory corruption in the client process, disclosure of adjacent heap memory, or termination of the process.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2026-93393?

It affects 1 product.


Products: Mongodb C Driver.

## How do I fix CVE-2026-93393?

Upgrade to a fixed version.

## Is CVE-2026-93393 being exploited?

There is no known exploitation of CVE-2026-93393 in the wild and no public exploit code.

## Other vulnerabilities in MongoDB Inc. C Driver

- [CVE-2026-6691](https://insights.sbomify.com/CVE-2026-6691/): MongoDB C Driver Cyrus SASL Canonicalization Buffer Overflow (high 8.6)
- [CVE-2026-84964](https://insights.sbomify.com/CVE-2026-84964/): Heap corruption via OCSP request double free from crafted multi-URL certificate in TLS client (high 8.2)
- [CVE-2024-7553](https://insights.sbomify.com/CVE-2024-7553/): Accessing Untrusted Directory May Allow Local Privilege Escalation (high 7.3)
- [CVE-2026-93395](https://insights.sbomify.com/CVE-2026-93395/): Integer Underflow → Heap Out-of-Bounds Read in `bson_new_from_buffer() (medium 6.9)
- [CVE-2025-12119](https://insights.sbomify.com/CVE-2025-12119/): Bulk write with options may read invalid memory (medium 6.9)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-93393 and fix it if it is affected.

What it is: CVE-2026-93393 is a critical memory corruption vulnerability in MongoDB Inc. C Driver, published on 17 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-2026-93393 in the wild and no public exploit code.

Affected product: MongoDB Inc. C 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-2026-93393/ (Markdown: https://insights.sbomify.com/CVE-2026-93393/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-93393
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-93393
- OSV: https://osv.dev/vulnerability/CVE-2026-93393

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-93393/
Summaries are generated and may contain mistakes; the official description above is the record.