# CVE-2018-0136: Denial of service in Cisco Aggregation Services Router 9000 Series

> Remote attackers can cause denial of service on Cisco ASR 9000 routers by sending crafted IPv6 packets to Trident-based line cards.

- **Severity:** High 8.6 (`CVSS:3.1/AV:N/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:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 31 Jan 2018
- **Updated:** 2 Dec 2024
- **Also known as:** GHSA-4wcf-6qr4-2vx5

## What is CVE-2018-0136?

CVE-2018-0136 is a high-severity denial of service vulnerability in Cisco Ios Xr, published on 31 Jan 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the IPv6 subsystem of Cisco IOS XR Software Release 5.3.4 for the Cisco Aggregation Services Router (ASR) 9000 Series could allow an unauthenticated, remote attacker to trigger a reload of one or more Trident-based line cards, resulting in a denial of service (DoS) condition. The vulnerability is due to incorrect handling of IPv6 packets with a fragment header extension. An attacker could exploit this vulnerability by sending IPv6 packets designed to trigger the issue either to or through the Trident-based line card. A successful exploit could allow the attacker to trigger a reload of Trident-based line cards, resulting in a DoS during the period of time the line card takes to restart. This vulnerability affects Cisco Aggregation Services Router (ASR) 9000 Series when the following conditions are met: The router is running Cisco IOS XR Software Release 5.3.4, and the router has installed Trident-based line cards that have IPv6 configured. A software maintenance upgrade (SMU) has been made available that addresses this vulnerability. The fix has also been incorporated into service pack 7 for Cisco IOS XR Software Release 5.3.4. Cisco Bug IDs: CSCvg46800.

Weakness: CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2018-0136?

It affects 1 product.


Products: Cisco Ios Xr.

## How do I fix CVE-2018-0136?

No fix has been published for CVE-2018-0136 yet. Limit exposure of the affected software until one is available.

## Is CVE-2018-0136 being exploited?

There is no known exploitation of CVE-2018-0136 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Ios Xr

- [CVE-2020-3118](https://insights.sbomify.com/CVE-2020-3118/): Cisco IOS XR Software Discovery Protocol Format String (high 8.8, exploited in the wild)
- [CVE-2020-3569](https://insights.sbomify.com/CVE-2020-3569/): Cisco IOS XR Software DVMRP Memory Exhaustion (high 8.6, exploited in the wild)
- [CVE-2020-3566](https://insights.sbomify.com/CVE-2020-3566/): Cisco IOS XR Software DVMRP Memory Exhaustion (high 8.6, exploited in the wild)
- [CVE-2010-3035](https://insights.sbomify.com/CVE-2010-3035/): Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service (high 7.5, exploited in the wild)
- [CVE-2022-20821](https://insights.sbomify.com/CVE-2022-20821/): Cisco IOS XR Open Port (medium 6.5, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-0136 and fix it if it is affected.

What it is: CVE-2018-0136 is a high-severity denial of service vulnerability in Cisco Ios Xr, published on 31 Jan 2018. 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-2018-0136 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-2018-0136/ (Markdown: https://insights.sbomify.com/CVE-2018-0136/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-0136
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-0136
- OSV: https://osv.dev/vulnerability/CVE-2018-0136

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-0136/
Summaries are generated and may contain mistakes; the official description above is the record.