# CVE-2016-6406: Auth bypass in n/a

> Remote attackers can gain root access via a testing interface if an outdated Enrollment Client is installed on Cisco ESA devices.

- **Severity:** Critical 9.8 (`CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 22 Sep 2016
- **Updated:** 6 Aug 2024
- **Also known as:** GHSA-vp5v-r76g-m4mx

## What is CVE-2016-6406?

CVE-2016-6406 is a critical authentication bypass vulnerability in n/a, published on 22 Sep 2016. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Cisco IronPort AsyncOS 9.1.2-023, 9.1.2-028, 9.1.2-036, 9.7.2-046, 9.7.2-047, 9.7.2-054, 10.0.0-124, and 10.0.0-125 on Email Security Appliance (ESA) devices, when Enrollment Client before 1.0.2-065 is installed, allows remote attackers to obtain root access via a connection to the testing/debugging interface, aka Bug ID CSCvb26017.

Weakness: CWE-264

## Which versions are affected by CVE-2016-6406?

It affects 1 product.


Products: Cisco Email Security Appliance Firmware.

## How do I fix CVE-2016-6406?

No fix has been published for CVE-2016-6406 yet. Limit exposure of the affected software until one is available.

## Is CVE-2016-6406 being exploited?

There is no known exploitation of CVE-2016-6406 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2018-15453](https://insights.sbomify.com/CVE-2018-15453/): Cisco Email Security Appliance Memory Corruption Denial of Service Vulnerability (high 8.6)
- [CVE-2017-6671](https://insights.sbomify.com/CVE-2017-6671/): Security feature bypass in Cisco Email Security Appliance (high 7.5)
- [CVE-2016-6458](https://insights.sbomify.com/CVE-2016-6458/): Security feature bypass in Cisco AsyncOS 10.0.0-125 and 9.7.1-066 (high 7.5)
- [CVE-2019-12706](https://insights.sbomify.com/CVE-2019-12706/): Cisco Email Security Appliance Filter Bypass Vulnerability (medium 6.5)
- [CVE-2019-15971](https://insights.sbomify.com/CVE-2019-15971/): Cisco Email Security Appliance MP3 Content Filter Bypass Vulnerability (medium 5.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-6406 and fix it if it is affected.

What it is: CVE-2016-6406 is a critical authentication bypass vulnerability in n/a, published on 22 Sep 2016. 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-2016-6406 in the wild and no public exploit code.

Affected product: n/a. 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-2016-6406/ (Markdown: https://insights.sbomify.com/CVE-2016-6406/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-6406
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-6406
- OSV: https://osv.dev/vulnerability/CVE-2016-6406

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-6406/
Summaries are generated and may contain mistakes; the official description above is the record.