# CVE-2016-6259: Denial of service in n/a

> Local 32-bit PV guest kernels can crash the hypervisor and VMs by triggering a safety check due to missing SMAP whitelisting.

- **Severity:** Medium 6.2 (`CVSS:3.0/AV:L/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 2 Aug 2016
- **Updated:** 6 Aug 2024
- **Also known as:** ALPINE-CVE-2016-6259, DEBIAN-CVE-2016-6259, GHSA-prj4-495w-f4qv, UBUNTU-CVE-2016-6259

## What is CVE-2016-6259?

CVE-2016-6259 is a medium-severity denial of service vulnerability in Citrix Xenserver, published on 2 Aug 2016. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Xen 4.5.x through 4.7.x do not implement Supervisor Mode Access Prevention (SMAP) whitelisting in 32-bit exception and event delivery, which allows local 32-bit PV guest OS kernels to cause a denial of service (hypervisor and VM crash) by triggering a safety check.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2016-6259?

It affects 2 products.


Products: Citrix Xenserver, Xen Xen.

## How do I fix CVE-2016-6259?

Apply the vendor's patch.

## Is CVE-2016-6259 being exploited?

There is no known exploitation of CVE-2016-6259 in the wild and no public exploit code.

## Other vulnerabilities in Citrix Xenserver

- [CVE-2014-4947](https://insights.sbomify.com/CVE-2014-4947/): Memory corruption in n/a (critical 10.0)
- [CVE-2018-14007](https://insights.sbomify.com/CVE-2018-14007/): Path traversal in n/a (critical 9.8)
- [CVE-2015-7705](https://insights.sbomify.com/CVE-2015-7705/): Denial of service in n/a (critical 9.8)
- [CVE-2016-5302](https://insights.sbomify.com/CVE-2016-5302/): Auth bypass in n/a (critical 9.8)
- [CVE-2017-12134](https://insights.sbomify.com/CVE-2017-12134/): Memory corruption in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-6259 and fix it if it is affected.

What it is: CVE-2016-6259 is a medium-severity denial of service vulnerability in Citrix Xenserver, published on 2 Aug 2016. 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-2016-6259 in the wild and no public exploit code.

Affected product: Citrix Xenserver. 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-2016-6259/ (Markdown: https://insights.sbomify.com/CVE-2016-6259/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-6259
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-6259
- OSV: https://osv.dev/vulnerability/CVE-2016-6259

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-6259/
Summaries are generated and may contain mistakes; the official description above is the record.