# CVE-2026-9100: Heap memory out of bounds read and crash in C Driver legacy GridFS file reader

> Attackers can crash applications or leak memory by providing malformed GridFS metadata to the MongoDB C Driver legacy API.

- **Severity:** Medium 6.0 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:N/VA:H/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:** 20 May 2026
- **Updated:** 20 May 2026
- **Also known as:** DEBIAN-CVE-2026-9100, GHSA-87jr-c2qj-3qrg, UBUNTU-CVE-2026-9100

## What is CVE-2026-9100?

CVE-2026-9100 is a medium-severity memory corruption vulnerability in MongoDB, Inc. C Driver, published on 20 May 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

The MongoDB C Driver's legacy GridFS API accepts malformed file metadata from the database without adequate validation. Crafted documents in a GridFS collection may cause any application that reads those files via the legacy API to either crash (via a division-by-zero) or silently leak process memory contents (via an out-of-bounds read).

Weakness: CWE-1285 (Improper Validation of Specified Index, Position, or Offset in Input)

## Which versions are affected by CVE-2026-9100?

It affects 1 product.


Products: Mongodb C Driver.

## How do I fix CVE-2026-9100?

Apply the vendor's patch.

## Is CVE-2026-9100 being exploited?

There is no known exploitation of CVE-2026-9100 in the wild and no public exploit code.

## Other vulnerabilities in MongoDB, Inc. 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-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)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-9100 and fix it if it is affected.

What it is: CVE-2026-9100 is a medium-severity memory corruption vulnerability in MongoDB, Inc. C Driver, published on 20 May 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-2026-9100 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-2026-9100/ (Markdown: https://insights.sbomify.com/CVE-2026-9100/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-9100
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-9100
- OSV: https://osv.dev/vulnerability/CVE-2026-9100

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-9100/
Summaries are generated and may contain mistakes; the official description above is the record.