# CVE-2026-88035: Heap buffer overflow via wrapped size check during SASL username canonicalization in MongoDB C Driver

> An integer overflow in the MongoDB C Driver allows a denial of service via heap buffer overflow when using optional SASL authentication.

- **Severity:** Medium 5.7 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 10 Sep 2026
- **Updated:** 10 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-88035, GHSA-jgj9-g5rr-w8xg, UBUNTU-CVE-2026-88035

## What is CVE-2026-88035?

CVE-2026-88035 is a medium-severity vulnerability in MongoDB C Driver, published on 10 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A size check in the client-side authentication path of the MongoDB C Driver can wrap around, so an unusually large user-name value is accepted and copied past the end of a small buffer. A party able to set the driver's connection settings may cause the application that embeds the driver to terminate unexpectedly. Reaching this code requires a build in which the optional external SASL authentication backend is present and a connection configured to use it.

Weakness: CWE-190 (Integer Overflow or Wraparound)

## Which versions are affected by CVE-2026-88035?

It affects 1 product.


Products: Mongodb C Driver.

## How do I fix CVE-2026-88035?

Apply the vendor's patch.

## Is CVE-2026-88035 being exploited?

There is no known exploitation of CVE-2026-88035 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-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-2026-88035 and fix it if it is affected.

What it is: CVE-2026-88035 is a medium-severity vulnerability in MongoDB C Driver, published on 10 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-88035 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-2026-88035/ (Markdown: https://insights.sbomify.com/CVE-2026-88035/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-88035
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-88035
- OSV: https://osv.dev/vulnerability/CVE-2026-88035

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-88035/
Summaries are generated and may contain mistakes; the official description above is the record.