# CVE-2018-0156: Cisco IOS Software and Cisco IOS XE Software Smart Install Denial-of-Service

> Unauthenticated remote attackers can cause a denial of service on Cisco IOS devices by sending crafted packets to Smart Install clients.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Yes, since 3 Mar 2022 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 28 Mar 2018
- **Updated:** 12 Jan 2026
- **Also known as:** GHSA-25w3-v3vx-g29w

## What is CVE-2018-0156?

CVE-2018-0156 is a high-severity denial of service vulnerability in Cisco Ios, published on 28 Mar 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the Smart Install feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to trigger a reload of an affected device, resulting in a denial of service (DoS) condition. The vulnerability is due to improper validation of packet data. An attacker could exploit this vulnerability by sending a crafted packet to an affected device on TCP port 4786. Only Smart Install client switches are affected. Cisco devices that are configured as a Smart Install director are not affected by this vulnerability. Cisco Bug IDs: CSCvd40673.

Weakness: CWE-20 (Improper Input Validation), CWE-399

## Which versions are affected by CVE-2018-0156?

It affects 2 products.


Products: Cisco Ios, Cisco Ios Xe.

## How do I fix CVE-2018-0156?

No fix has been published for CVE-2018-0156 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 17 Mar 2022.

## Is CVE-2018-0156 being exploited?

Yes. Attackers have exploited CVE-2018-0156 in the wild since at least 3 Mar 2022.

## Other vulnerabilities in Cisco Ios

- [CVE-2017-12240](https://insights.sbomify.com/CVE-2017-12240/): Cisco IOS and IOS XE Software DHCP Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2017-3881](https://insights.sbomify.com/CVE-2017-3881/): Cisco IOS and IOS XE Remote Code Execution (critical 9.8, exploited in the wild)
- [CVE-2018-0167](https://insights.sbomify.com/CVE-2018-0167/): Cisco IOS, XR, and XE Software Buffer Overflow (high 8.8, exploited in the wild)
- [CVE-2017-6736](https://insights.sbomify.com/CVE-2017-6736/): Cisco IOS and IOS XE Software SNMP Remote Code Execution (high 8.8, exploited in the wild)
- [CVE-2017-6737](https://insights.sbomify.com/CVE-2017-6737/): Cisco IOS and IOS XE Software SNMP Remote Code Execution (high 8.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2018-0156 and fix it if it is affected.

What it is: CVE-2018-0156 is a high-severity denial of service vulnerability in Cisco Ios, published on 28 Mar 2018. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2018-0156 in the wild since at least 3 Mar 2022.

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-2018-0156/ (Markdown: https://insights.sbomify.com/CVE-2018-0156/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2018-0156
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2018-0156
- OSV: https://osv.dev/vulnerability/CVE-2018-0156

---
From sbomify Insights: https://insights.sbomify.com/CVE-2018-0156/
Summaries are generated and may contain mistakes; the official description above is the record.