# CVE-2026-84964: Heap corruption via OCSP request double free from crafted multi-URL certificate in TLS client

> A malicious trusted TLS endpoint can trigger a double free in the MongoDB C Driver, causing the client application to crash.

- **Severity:** High 8.2 (`CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:N/VI:N/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:** 3 Sep 2026
- **Updated:** 3 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-84964, UBUNTU-CVE-2026-84964

## What is CVE-2026-84964?

CVE-2026-84964 is a high-severity use after free vulnerability in MongoDB C 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

A double free in the OpenSSL-based TLS certificate revocation checking path of the MongoDB C Driver can be reached by a TLS endpoint that the client already trusts. During the handshake, specially formed certificate data can cause the same heap object to be released twice. An unauthenticated party acting as the trusted endpoint may cause the connecting client application to terminate unexpectedly.

Weakness: CWE-415 (Double Free)

## Which versions are affected by CVE-2026-84964?

It affects 1 product.


Products: Mongodb C Driver.

## How do I fix CVE-2026-84964?

Upgrade to a fixed version.

## Is CVE-2026-84964 being exploited?

There is no known exploitation of CVE-2026-84964 in the wild and no public exploit code.

## Other vulnerabilities in MongoDB C Driver

- [CVE-2026-93393](https://insights.sbomify.com/CVE-2026-93393/): Heap overflow via oversized decrypted TLS record sequence in Windows Secure Channel stream (critical 9.2)
- [CVE-2026-6691](https://insights.sbomify.com/CVE-2026-6691/): MongoDB C Driver Cyrus SASL Canonicalization Buffer Overflow (high 8.6)
- [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-2026-84964 and fix it if it is affected.

What it is: CVE-2026-84964 is a high-severity use after free vulnerability in MongoDB C 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-2026-84964 in the wild and no public exploit code.

Affected product: MongoDB 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-2026-84964/ (Markdown: https://insights.sbomify.com/CVE-2026-84964/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-84964
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-84964
- OSV: https://osv.dev/vulnerability/CVE-2026-84964

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-84964/
Summaries are generated and may contain mistakes; the official description above is the record.