# CVE-2019-1918: Cisco IOS XR Software Intermediate System–to–Intermediate System Denial of Service Vulnerability

> An unauthenticated attacker in the same IS-IS area can cause a denial of service by sending malicious link-state PDUs to Cisco IOS XR devices.

- **Severity:** High 7.4 (`CVSS:3.0/AV:A/AC:L/PR:N/UI:N/S:C/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:** No
- **Published:** 7 Aug 2019
- **Updated:** 21 Nov 2024
- **Also known as:** GHSA-29rc-5w3j-4hr7

## What is CVE-2019-1918?

CVE-2019-1918 is a high-severity denial of service vulnerability in Cisco Ios Xr, published on 7 Aug 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 implementation of Intermediate System–to–Intermediate System (IS–IS) routing protocol functionality in Cisco IOS XR Software could allow an unauthenticated attacker who is in the same IS-IS area to cause a denial of service (DoS) condition. The vulnerability is due to incorrect processing of IS–IS link-state protocol data units (PDUs). An attacker could exploit this vulnerability by sending specific link-state PDUs to an affected system to be processed. A successful exploit could allow the attacker to cause incorrect calculations used in the weighted remote shared risk link groups (SRLG) or in the IGP Flexible Algorithm. It could also cause tracebacks to the logs or potentially cause the receiving device to crash the IS–IS process, resulting in a DoS condition.

Weakness: CWE-682 (Incorrect Calculation), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2019-1918?

It affects 2 products.


Products: Cisco Carrier Routing System, Cisco Ios Xr.

## How do I fix CVE-2019-1918?

No fix has been published for CVE-2019-1918 yet. Limit exposure of the affected software until one is available.

## Is CVE-2019-1918 being exploited?

There is no known exploitation of CVE-2019-1918 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Ios Xr

- [CVE-2018-0132](https://insights.sbomify.com/CVE-2018-0132/): Denial of service in Cisco IOS XR (high 8.6)
- [CVE-2019-1910](https://insights.sbomify.com/CVE-2019-1910/): Cisco IOS XR Software Intermediate System to Intermediate System Denial of Service Vulnerability (high 7.4)
- [CVE-2015-0618](https://insights.sbomify.com/CVE-2015-0618/): Denial of service in n/a (high 7.1)
- [CVE-2012-1342](https://insights.sbomify.com/CVE-2012-1342/): Security feature bypass in n/a (medium 5.8)
- [CVE-2016-6401](https://insights.sbomify.com/CVE-2016-6401/): Denial of service in n/a (medium 5.3)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2019-1918 and fix it if it is affected.

What it is: CVE-2019-1918 is a high-severity denial of service vulnerability in Cisco Ios Xr, published on 7 Aug 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-2019-1918 in the wild and no public exploit code.

Affected product: Cisco Ios Xr. 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-2019-1918/ (Markdown: https://insights.sbomify.com/CVE-2019-1918/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2019-1918
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2019-1918
- OSV: https://osv.dev/vulnerability/CVE-2019-1918

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From sbomify Insights: https://insights.sbomify.com/CVE-2019-1918/
Summaries are generated and may contain mistakes; the official description above is the record.