# CVE-2006-6696: Use after free in n/a

> Local attackers can escalate privileges by triggering a double free in CSRSS via crafted MessageBox calls in Microsoft Windows.

- **Severity:** Medium 6.9 (`AV:L/AC:M/Au:N/C:C/I:C/A:C`)
- **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:** No
- **Published:** 22 Dec 2006
- **Updated:** 7 Aug 2024
- **Also known as:** GHSA-fmp2-4wcx-jwx4

## What is CVE-2006-6696?

CVE-2006-6696 is a medium-severity use after free vulnerability in Microsoft Windows 2000, published on 22 Dec 2006. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Double free vulnerability in Microsoft Windows 2000, XP, 2003, and Vista allows local users to gain privileges by calling the MessageBox function with a MB_SERVICE_NOTIFICATION message with crafted data, which sends a HardError message to Client/Server Runtime Server Subsystem (CSRSS) process, which is not properly handled when invoking the UserHardError and GetHardErrorText functions in WINSRV.DLL.

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2006-6696?

It affects 4 products.


Products: Microsoft Windows 2000, Microsoft Windows 2003 Server, Microsoft Windows Vista, Microsoft Windows Xp.

## How do I fix CVE-2006-6696?

No fix has been published for CVE-2006-6696 yet. Limit exposure of the affected software until one is available.

## Is CVE-2006-6696 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2006-6696 exists.

Public exploit code:

- Microsoft Windows - 'MessageBox' Memory Corruption Local Denial of Service (exploitdb)
- Microsoft Windows - NtRaiseHardError 'Csrss.exe' Memory Disclosure (exploitdb)

## Other vulnerabilities in Microsoft Windows 2000

- [CVE-2008-4250](https://insights.sbomify.com/CVE-2008-4250/): Microsoft Windows Buffer Overflow (critical 9.8, exploited in the wild)
- [CVE-2010-0232](https://insights.sbomify.com/CVE-2010-0232/): Microsoft Windows Kernel Exception Handler (high 7.8, exploited in the wild)
- [CVE-2009-1123](https://insights.sbomify.com/CVE-2009-1123/): Microsoft Windows Improper Input Validation (high 7.8, exploited in the wild)
- [CVE-2002-0367](https://insights.sbomify.com/CVE-2002-0367/): Microsoft Windows Privilege Escalation (high 7.8, exploited in the wild)
- [CVE-2010-0269](https://insights.sbomify.com/CVE-2010-0269/): Memory corruption in n/a (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2006-6696 and fix it if it is affected.

What it is: CVE-2006-6696 is a medium-severity use after free vulnerability in Microsoft Windows 2000, published on 22 Dec 2006. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2006-6696 exists.

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-2006-6696/ (Markdown: https://insights.sbomify.com/CVE-2006-6696/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2006-6696
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2006-6696
- OSV: https://osv.dev/vulnerability/CVE-2006-6696

---
From sbomify Insights: https://insights.sbomify.com/CVE-2006-6696/
Summaries are generated and may contain mistakes; the official description above is the record.