# CVE-2017-12240: Cisco IOS and IOS XE Software DHCP Remote Code Execution

> Remote attackers can execute arbitrary code or cause denial of service via crafted DHCPv4 packets in Cisco IOS DHCP relay.

- **Severity:** Critical 9.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/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 Sep 2017
- **Updated:** 12 Jan 2026
- **Also known as:** GHSA-q8rh-r33q-hvj2

## What is CVE-2017-12240?

CVE-2017-12240 is a critical memory corruption vulnerability in Cisco Ios, published on 28 Sep 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

The DHCP relay subsystem of Cisco IOS 12.2 through 15.6 and Cisco IOS XE Software contains a vulnerability that could allow an unauthenticated, remote attacker to execute arbitrary code and gain full control of an affected system. The attacker could also cause an affected system to reload, resulting in a denial of service (DoS) condition. The vulnerability is due to a buffer overflow condition in the DHCP relay subsystem of the affected software. An attacker could exploit this vulnerability by sending a crafted DHCP Version 4 (DHCPv4) packet to an affected system. A successful exploit could allow the attacker to execute arbitrary code and gain full control of the affected system or cause the affected system to reload, resulting in a DoS condition. Cisco Bug IDs: CSCsm45390, CSCuw77959.

Weakness: CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer), CWE-20 (Improper Input Validation)

## Which versions are affected by CVE-2017-12240?

It affects 1 product.


Products: Cisco Ios.

## How do I fix CVE-2017-12240?

No fix has been published for CVE-2017-12240 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 24 Mar 2022.

## Is CVE-2017-12240 being exploited?

Yes. Attackers have exploited CVE-2017-12240 in the wild since at least 3 Mar 2022.

## Other vulnerabilities in Cisco Ios

- [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)
- [CVE-2017-6738](https://insights.sbomify.com/CVE-2017-6738/): 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-2017-12240 and fix it if it is affected.

What it is: CVE-2017-12240 is a critical memory corruption vulnerability in Cisco Ios, published on 28 Sep 2017. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2017-12240 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-2017-12240/ (Markdown: https://insights.sbomify.com/CVE-2017-12240/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2017-12240
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2017-12240
- OSV: https://osv.dev/vulnerability/CVE-2017-12240

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From sbomify Insights: https://insights.sbomify.com/CVE-2017-12240/
Summaries are generated and may contain mistakes; the official description above is the record.