# CVE-1999-0391: Auth bypass in n/a

> An attacker can replay SMB authentication challenges to impersonate users on Windows 95 and 98 systems.

- **Severity:** High 7.5 (`AV:N/AC:L/Au:N/C:P/I:P/A:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 29 Sep 1999
- **Updated:** 1 Aug 2024
- **Also known as:** GHSA-9xx2-9vgq-cg78

## What is CVE-1999-0391?

CVE-1999-0391 is a high-severity authentication bypass vulnerability in Microsoft Windows 2000, published on 29 Sep 1999. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The cryptographic challenge of SMB authentication in Windows 95 and Windows 98 can be reused, allowing an attacker to replay the response and impersonate a user.

## Which versions are affected by CVE-1999-0391?

It affects 3 products.


Products: Microsoft Terminal Server, Microsoft Windows 2000, Microsoft Windows Nt.

## How do I fix CVE-1999-0391?

No fix has been published for CVE-1999-0391 yet. Limit exposure of the affected software until one is available.

## Is CVE-1999-0391 being exploited?

There is no known exploitation of CVE-1999-0391 in the wild and no public exploit code.

## Other vulnerabilities in Microsoft Windows 2000

- [CVE-2006-4465](https://insights.sbomify.com/CVE-2006-4465/): Code injection in n/a (critical 10.0)
- [CVE-2007-2593](https://insights.sbomify.com/CVE-2007-2593/): Security feature bypass in n/a (high 7.5)
- [CVE-1999-0909](https://insights.sbomify.com/CVE-1999-0909/): Security feature bypass in n/a (high 7.5)
- [CVE-2000-0259](https://insights.sbomify.com/CVE-2000-0259/): The default permissions for the Cryptography\Offload registry key used by the OffloadModExpo in Windows NT 4.0 allows local users to obtain (high 7.2)
- [CVE-2001-0540](https://insights.sbomify.com/CVE-2001-0540/): Denial of service in n/a (medium 5.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-1999-0391 and fix it if it is affected.

What it is: CVE-1999-0391 is a high-severity authentication bypass vulnerability in Microsoft Windows 2000, published on 29 Sep 1999. 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-1999-0391 in the wild and no public exploit code.

Affected product: Microsoft Windows 2000. 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-1999-0391/ (Markdown: https://insights.sbomify.com/CVE-1999-0391/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-1999-0391
- NVD: https://nvd.nist.gov/vuln/detail/CVE-1999-0391
- OSV: https://osv.dev/vulnerability/CVE-1999-0391

---
From sbomify Insights: https://insights.sbomify.com/CVE-1999-0391/
Summaries are generated and may contain mistakes; the official description above is the record.