# CVE-2017-3859: Denial of service in Cisco IOS XE Software for Cisco ASR 920 Series Routers

> Remote attackers can cause a denial of service on Cisco ASR 920 routers by sending crafted DHCP packets if the DHCP server port is enabled.

- **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:** 22 Mar 2017
- **Updated:** 5 Aug 2024
- **Also known as:** GHSA-6xvc-57g8-cq77

## What is CVE-2017-3859?

CVE-2017-3859 is a high-severity denial of service vulnerability in Cisco Ios Xe, published on 22 Mar 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the DHCP code for the Zero Touch Provisioning feature of Cisco ASR 920 Series Aggregation Services Routers could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to a format string vulnerability when processing a crafted DHCP packet for Zero Touch Provisioning. An attacker could exploit this vulnerability by sending a specially crafted DHCP packet to an affected device. An exploit could allow the attacker to cause the device to reload, resulting in a denial of service (DoS) condition. This vulnerability affects Cisco ASR 920 Series Aggregation Services Routers that are running an affected release of Cisco IOS XE Software (3.13 through 3.18) and are listening on the DHCP server port. By default, the devices do not listen on the DHCP server port. Cisco Bug IDs: CSCuy56385.

Weakness: CWE-134 (Use of Externally-Controlled Format String)

## Which versions are affected by CVE-2017-3859?

It affects 1 product.


Products: Cisco Ios Xe.

## How do I fix CVE-2017-3859?

No fix has been published for CVE-2017-3859 yet. Limit exposure of the affected software until one is available.

## Is CVE-2017-3859 being exploited?

There is no known exploitation of CVE-2017-3859 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-2017-3859 and fix it if it is affected.

What it is: CVE-2017-3859 is a high-severity denial of service vulnerability in Cisco Ios Xe, published on 22 Mar 2017. 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-2017-3859 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-2017-3859/ (Markdown: https://insights.sbomify.com/CVE-2017-3859/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-3859
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-3859
- OSV: https://osv.dev/vulnerability/CVE-2017-3859

---
From sbomify Insights: https://insights.sbomify.com/CVE-2017-3859/
Summaries are generated and may contain mistakes; the official description above is the record.