# CVE-2026-81517: MongoDB Connector for BI Improper Error Handling of Log Write Failures May Cause Loss of SQL Service

> An unauthenticated attacker can exhaust log storage to crash the MongoDB BI Connector, causing a denial of service for all SQL clients.

- **Severity:** High 8.7 (`CVSS:4.0/AV:N/AC:L/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:** No
- **Published:** 28 Aug 2026
- **Updated:** 31 Aug 2026
- **Also known as:** GHSA-87fw-525c-9h5m

## What is CVE-2026-81517?

CVE-2026-81517 is a high-severity denial of service vulnerability in MongoDB BI Connector, published on 28 Aug 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

An unauthenticated party able to reach the port of a MongoDB Connector for BI (mongosqld) instance may generate enough routine connection log activity to exhaust the storage backing the configured log path. When a log write or log rotation operation subsequently fails, the resulting error is not handled and the shared mongosqld process ends, ending service for all connected SQL clients. The process continues to end on startup until an operator restores available storage, and the diagnostic message explaining the condition is not recorded.

Weakness: CWE-248 (Uncaught Exception)

## Which versions are affected by CVE-2026-81517?

It affects 1 product.


Products: Mongodb Bi Connector.

## How do I fix CVE-2026-81517?

No fix has been published for CVE-2026-81517 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-81517 being exploited?

There is no known exploitation of CVE-2026-81517 in the wild and no public exploit code.

## Other vulnerabilities in MongoDB BI Connector

- [CVE-2026-81518](https://insights.sbomify.com/CVE-2026-81518/): BI Connector Optional Client Certificate Verification Allows Unauthenticated Connections (high 8.7)
- [CVE-2026-81520](https://insights.sbomify.com/CVE-2026-81520/): MongoDB Connector for BI Unbounded Authentication Negotiation Leading to Connection Exhaustion (high 8.7)
- [CVE-2026-77586](https://insights.sbomify.com/CVE-2026-77586/): MongoDB Connector for BI Unescaped Object Names in Generated SHOW CREATE Output (high 8.5)
- [CVE-2026-81490](https://insights.sbomify.com/CVE-2026-81490/): MongoDB Connector for BI Improper Error Handling During Schema Sampling May Cause Loss of SQL Service (high 8.3)
- [CVE-2026-75159](https://insights.sbomify.com/CVE-2026-75159/): MongoDB BI Connector Improper Memory Handling During Failed Kerberos Authentication May Cause Process Termination (high 8.2)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-81517 and fix it if it is affected.

What it is: CVE-2026-81517 is a high-severity denial of service vulnerability in MongoDB BI Connector, published on 28 Aug 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-2026-81517 in the wild and no public exploit code.

Affected product: MongoDB BI Connector. 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-2026-81517/ (Markdown: https://insights.sbomify.com/CVE-2026-81517/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-81517
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-81517
- OSV: https://osv.dev/vulnerability/CVE-2026-81517

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-81517/
Summaries are generated and may contain mistakes; the official description above is the record.