# CVE-2019-12656: Cisco IOx Application Environment Denial of Service Vulnerability

> Unauthenticated remote attackers can cause a denial of service in Cisco IOx web servers by sending crafted TLS packets.

- **Severity:** High 7.5 (`CVSS:3.0/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 25 Sep 2019
- **Updated:** 19 Nov 2024
- **Also known as:** GHSA-6r46-67j7-hr8v

## What is CVE-2019-12656?

CVE-2019-12656 is a high-severity denial of service vulnerability in Cisco Ios, published on 25 Sep 2019. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the IOx application environment of multiple Cisco platforms could allow an unauthenticated, remote attacker to cause the IOx web server to stop processing HTTPS requests, resulting in a denial of service (DoS) condition. The vulnerability is due to a Transport Layer Security (TLS) implementation issue. An attacker could exploit this vulnerability by sending crafted TLS packets to the IOx web server on an affected device. A successful exploit could allow the attacker to cause the IOx web server to stop processing HTTPS requests, resulting in a DoS condition.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2019-12656?

It affects 6 products.


Products: Cisco Cgr 1000 Firmware, Cisco Ic3000 Firmware, Cisco Ie 4000 Firmware, Cisco Industrial Ethernet 2000 Series Firmware, Cisco Ios, Cisco Ir510 Wpan Firmware.

## How do I fix CVE-2019-12656?

No fix has been published for CVE-2019-12656 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-12656 being exploited?

There is no known exploitation of CVE-2019-12656 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-12656 and fix it if it is affected.

What it is: CVE-2019-12656 is a high-severity denial of service vulnerability in Cisco Ios, published on 25 Sep 2019. 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-2019-12656 in the wild and no public exploit code.

Affected product: Cisco Ios. 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-2019-12656/ (Markdown: https://insights.sbomify.com/CVE-2019-12656/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-12656
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-12656
- OSV: https://osv.dev/vulnerability/CVE-2019-12656

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From sbomify Insights: https://insights.sbomify.com/CVE-2019-12656/
Summaries are generated and may contain mistakes; the official description above is the record.