# CVE-2016-6366: Cisco Adaptive Security Appliance (ASA) SNMP Buffer Overflow

> Remote authenticated attackers can execute arbitrary code on Cisco ASA devices via crafted SNMP packets, requiring immediate patching.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Yes, since 24 May 2022 (CISA KEV)
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 18 Aug 2016
- **Updated:** 12 Jan 2026
- **Also known as:** GHSA-pfgh-2mw6-962h

## What is CVE-2016-6366?

CVE-2016-6366 is a high-severity memory corruption vulnerability in Cisco Adaptive Security Appliance Software, published on 18 Aug 2016. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Buffer overflow in Cisco Adaptive Security Appliance (ASA) Software through 9.4.2.3 on ASA 5500, ASA 5500-X, ASA Services Module, ASA 1000V, ASAv, Firepower 9300 ASA Security Module, PIX, and FWSM devices allows remote authenticated users to execute arbitrary code via crafted IPv4 SNMP packets, aka Bug ID CSCva92151 or EXTRABACON.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2016-6366?

It affects 3 products.


Products: Cisco Adaptive Security Appliance Software, Cisco Asa 1000v Cloud Firewall Software, Cisco Pix Firewall Software.

## How do I fix CVE-2016-6366?

No fix has been published for CVE-2016-6366 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 14 Jun 2022.

## Is CVE-2016-6366 being exploited?

Yes. Attackers have exploited CVE-2016-6366 in the wild since at least 24 May 2022.

Public exploit code:

- Public repository for improvements to the EXTRABACON exploit (github_poc): https://github.com/RiskSense-Ops/CVE-2016-6366
- Cisco ASA 8.x - 'EXTRABACON' Authentication Bypass (exploitdb)
- Cisco ASA Authentication Bypass (EXTRABACON) (metasploit)

## Other vulnerabilities in Cisco Adaptive Security Appliance Software

- [CVE-2025-20333](https://insights.sbomify.com/CVE-2025-20333/): Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Buffer Overflow (critical 9.9, exploited in the wild)
- [CVE-2026-20349](https://insights.sbomify.com/CVE-2026-20349/): Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection (high 8.6, exploited in the wild)
- [CVE-2024-20353](https://insights.sbomify.com/CVE-2024-20353/): Cisco ASA and FTD Denial of Service (high 8.6, exploited in the wild)
- [CVE-2016-6367](https://insights.sbomify.com/CVE-2016-6367/): Cisco Adaptive Security Appliance (ASA) CLI Remote Code Execution (high 7.8, exploited in the wild)
- [CVE-2020-3452](https://insights.sbomify.com/CVE-2020-3452/): Cisco ASA and FTD Read-Only Path Traversal (high 7.5, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2016-6366 and fix it if it is affected.

What it is: CVE-2016-6366 is a high-severity memory corruption vulnerability in Cisco Adaptive Security Appliance Software, published on 18 Aug 2016. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2016-6366 in the wild since at least 24 May 2022.

Affected product: Cisco Adaptive Security Appliance Software. 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-2016-6366/ (Markdown: https://insights.sbomify.com/CVE-2016-6366/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2016-6366
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2016-6366
- OSV: https://osv.dev/vulnerability/CVE-2016-6366

---
From sbomify Insights: https://insights.sbomify.com/CVE-2016-6366/
Summaries are generated and may contain mistakes; the official description above is the record.