# CVE-2021-34727: Cisco IOS XE SD-WAN Software Buffer Overflow Vulnerability

> Unauthenticated remote attackers can trigger a buffer overflow in Cisco IOS XE SD-WAN devices to execute arbitrary commands with root privileges or cause a denial of service.

- **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:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 23 Sep 2021
- **Updated:** 7 Nov 2024
- **Also known as:** GHSA-rxw2-fh82-mfcc

## What is CVE-2021-34727?

CVE-2021-34727 is a critical memory corruption vulnerability in Cisco IOS XE SD-WAN Software, published on 23 Sep 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A vulnerability in the vDaemon process in Cisco IOS XE SD-WAN Software could allow an unauthenticated, remote attacker to cause a buffer overflow on an affected device. This vulnerability is due to insufficient bounds checking when an affected device processes traffic. An attacker could exploit this vulnerability by sending crafted traffic to the device. A successful exploit could allow the attacker to cause a buffer overflow and possibly execute arbitrary commands with root-level privileges, or cause the device to reload, which could result in a denial of service condition.

Weakness: CWE-120 (Buffer Copy without Checking Size of Input)

## Which versions are affected by CVE-2021-34727?

It affects 1 product.


Products: Cisco Ios Xe Sd-Wan.

## How do I fix CVE-2021-34727?

No fix has been published for CVE-2021-34727 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34727 being exploited?

There is no known exploitation of CVE-2021-34727 in the wild and no public exploit code.

## Other vulnerabilities in Cisco IOS XE SD-WAN Software

- [CVE-2020-3375](https://insights.sbomify.com/CVE-2020-3375/): Cisco SD-WAN Solution Software Buffer Overflow Vulnerability (critical 9.8)
- [CVE-2021-1305](https://insights.sbomify.com/CVE-2021-1305/): Cisco SD-WAN vManage Authorization Bypass Vulnerabilities (high 8.8)
- [CVE-2023-20035](https://insights.sbomify.com/CVE-2023-20035/): Cisco IOS XE SD-WAN Software Command Injection Vulnerability (high 7.8)
- [CVE-2020-3216](https://insights.sbomify.com/CVE-2020-3216/): Cisco IOS XE SD-WAN Software Authentication Bypass Vulnerability (medium 6.8)
- [CVE-2021-34725](https://insights.sbomify.com/CVE-2021-34725/): Cisco IOS XE SD-WAN Software Command Injection Vulnerability (medium 6.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34727 and fix it if it is affected.

What it is: CVE-2021-34727 is a critical memory corruption vulnerability in Cisco IOS XE SD-WAN Software, published on 23 Sep 2021. 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-2021-34727 in the wild and no public exploit code.

Affected product: Cisco IOS XE SD-WAN Software. 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-2021-34727/ (Markdown: https://insights.sbomify.com/CVE-2021-34727/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34727
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34727
- OSV: https://osv.dev/vulnerability/CVE-2021-34727

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-34727/
Summaries are generated and may contain mistakes; the official description above is the record.