# CVE-2019-12664: Cisco IOS XE Software ISDN Data Leak Vulnerability

> An attacker can bypass PPP authentication to pass IPv4 traffic through an ISDN channel on Cisco IOS XE routers, exposing data.

- **Severity:** Medium 4.7 (`CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 25 Sep 2019
- **Updated:** 21 Nov 2024
- **Also known as:** GHSA-qf56-4c48-p66f

## What is CVE-2019-12664?

CVE-2019-12664 is a medium-severity authentication bypass vulnerability in Cisco Ios Xe, published on 25 Sep 2019. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A vulnerability in the Dialer interface feature for ISDN connections in Cisco IOS XE Software for Cisco 4000 Series Integrated Services Routers (ISRs) could allow an unauthenticated, adjacent attacker to pass IPv4 traffic through an ISDN channel prior to successful PPP authentication. The vulnerability is due to insufficient validation of the state of the PPP IP Control Protocol (IPCP). An attacker could exploit this vulnerability by making an ISDN call to an affected device and sending traffic through the ISDN channel prior to successful PPP authentication. Alternatively, an unauthenticated, remote attacker could exploit this vulnerability by sending traffic through an affected device that is configured to exit via an ISDN connection for which both the Dialer interface and the Basic Rate Interface (BRI) have been configured, but the Challenge Handshake Authentication Protocol (CHAP) password for PPP does not match the remote end. A successful exploit could allow the attacker to pass IPv4 traffic through an unauthenticated ISDN connection for a few seconds, from initial ISDN call setup until PPP authentication fails.

Weakness: CWE-287 (Improper Authentication), CWE-200 (Exposure of Sensitive Information to an Unauthorized Actor)

## Which versions are affected by CVE-2019-12664?

It affects 1 product.


Products: Cisco Ios Xe.

## How do I fix CVE-2019-12664?

No fix has been published for CVE-2019-12664 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-12664 being exploited?

There is no known exploitation of CVE-2019-12664 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Ios Xe

- [CVE-2023-20198](https://insights.sbomify.com/CVE-2023-20198/): Cisco IOS XE Web UI Privilege Escalation (critical 10.0, exploited in the wild)
- [CVE-2018-0151](https://insights.sbomify.com/CVE-2018-0151/): Cisco IOS Software and Cisco IOS XE Software Quality of Service Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2023-20273](https://insights.sbomify.com/CVE-2023-20273/): Cisco IOS XE Web UI Command Injection (high 7.2, exploited in the wild)
- [CVE-2025-20188](https://insights.sbomify.com/CVE-2025-20188/): Hardcoded credentials in Cisco IOS XE Software (critical 10.0)
- [CVE-2021-34770](https://insights.sbomify.com/CVE-2021-34770/): Cisco IOS XE Software for Catalyst 9000 Family Wireless Controllers CAPWAP Remote Code Execution Vulnerability (critical 10.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-12664 and fix it if it is affected.

What it is: CVE-2019-12664 is a medium-severity authentication bypass vulnerability in Cisco Ios Xe, published on 25 Sep 2019. 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-2019-12664 in the wild and no public exploit code.

Affected product: Cisco Ios Xe. 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-2019-12664/ (Markdown: https://insights.sbomify.com/CVE-2019-12664/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-12664
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-12664
- OSV: https://osv.dev/vulnerability/CVE-2019-12664

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From sbomify Insights: https://insights.sbomify.com/CVE-2019-12664/
Summaries are generated and may contain mistakes; the official description above is the record.