# CVE-2017-3856: Denial of service in Cisco IOS XE

> An unauthenticated remote attacker can cause a device reload by flooding the web interface, requiring the interface to be 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-998w-hghj-9wh4

## What is CVE-2017-3856?

CVE-2017-3856 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 web user interface of Cisco IOS XE 3.1 through 3.17 could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to insufficient resource handling by the affected software when the web user interface is under a high load. An attacker could exploit this vulnerability by sending a high number of requests to the web user interface of the affected software. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition. To exploit this vulnerability, the attacker must have access to the management interface of the affected software, which is typically connected to a restricted management network. This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS XE Software, if the web user interface of the software is enabled. By default, the web user interface is not enabled. Cisco Bug IDs: CSCup70353.

Weakness: CWE-400 (Uncontrolled Resource Consumption), CWE-399

## Which versions are affected by CVE-2017-3856?

It affects 1 product.


Products: Cisco Ios Xe.

## How do I fix CVE-2017-3856?

No fix has been published for CVE-2017-3856 yet. Limit exposure of the affected software until one is available.

## Is CVE-2017-3856 being exploited?

There is no known exploitation of CVE-2017-3856 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-2017-3856 and fix it if it is affected.

What it is: CVE-2017-3856 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-2017-3856 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-2017-3856/ (Markdown: https://insights.sbomify.com/CVE-2017-3856/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-3856
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-3856
- OSV: https://osv.dev/vulnerability/CVE-2017-3856

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From sbomify Insights: https://insights.sbomify.com/CVE-2017-3856/
Summaries are generated and may contain mistakes; the official description above is the record.