# CVE-2021-34718: Cisco IOS XR Software Arbitrary File Read and Write Vulnerability

> Authenticated attackers can read and write arbitrary files via SCP, leading to privilege escalation and unauthorized data access on Cisco IOS XR devices.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 9 Sep 2021
- **Updated:** 7 Nov 2024
- **Also known as:** GHSA-9j7c-3668-hr3c

## What is CVE-2021-34718?

CVE-2021-34718 is a high-severity path traversal vulnerability in Cisco Ios Xr, published on 9 Sep 2021. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

A vulnerability in the SSH Server process of Cisco IOS XR Software could allow an authenticated, remote attacker to overwrite and read arbitrary files on the local device. This vulnerability is due to insufficient input validation of arguments that are supplied by the user for a specific file transfer method. An attacker with lower-level privileges could exploit this vulnerability by specifying Secure Copy Protocol (SCP) parameters when authenticating to a device. A successful exploit could allow the attacker to elevate their privileges and retrieve and upload files on a device that they should not have access to.

Weakness: CWE-88 (Improper Neutralization of Argument Delimiters in a Command)

## Which versions are affected by CVE-2021-34718?

It affects 1 product.


Products: Cisco Ios Xr.

## How do I fix CVE-2021-34718?

No fix has been published for CVE-2021-34718 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-34718 being exploited?

There is no known exploitation of CVE-2021-34718 in the wild and no public exploit code.

## Other vulnerabilities in Cisco Ios Xr

- [CVE-2020-3118](https://insights.sbomify.com/CVE-2020-3118/): Cisco IOS XR Software Discovery Protocol Format String (high 8.8, exploited in the wild)
- [CVE-2020-3569](https://insights.sbomify.com/CVE-2020-3569/): Cisco IOS XR Software DVMRP Memory Exhaustion (high 8.6, exploited in the wild)
- [CVE-2020-3566](https://insights.sbomify.com/CVE-2020-3566/): Cisco IOS XR Software DVMRP Memory Exhaustion (high 8.6, exploited in the wild)
- [CVE-2010-3035](https://insights.sbomify.com/CVE-2010-3035/): Cisco IOS XR Border Gateway Protocol (BGP) Denial-of-Service (high 7.5, exploited in the wild)
- [CVE-2022-20821](https://insights.sbomify.com/CVE-2022-20821/): Cisco IOS XR Open Port (medium 6.5, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-34718 and fix it if it is affected.

What it is: CVE-2021-34718 is a high-severity path traversal vulnerability in Cisco Ios Xr, published on 9 Sep 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-34718 in the wild and no public exploit code.

Affected product: Cisco Ios Xr. 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-2021-34718/ (Markdown: https://insights.sbomify.com/CVE-2021-34718/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-34718
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-34718
- OSV: https://osv.dev/vulnerability/CVE-2021-34718

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-34718/
Summaries are generated and may contain mistakes; the official description above is the record.