# CVE-2021-28505: Security feature bypass in EOS

> Attackers can bypass IP protocol restrictions in access lists containing VXLAN rules on Arista EOS devices, potentially allowing unauthorized traffic.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 14 Apr 2022
- **Updated:** 16 Sep 2024
- **Also known as:** GHSA-3p5w-c6fg-w249

## What is CVE-2021-28505?

CVE-2021-28505 is a high-severity vulnerability in Arista Networks EOS, published on 14 Apr 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

On affected Arista EOS platforms, if a VXLAN match rule exists in an IPv4 access-list that is applied to the ingress of an L2 or an L3 port/SVI, the VXLAN rule and subsequent ACL rules in that access list will ignore the specified IP protocol.

Weakness: CWE-863 (Incorrect Authorization), CWE-284 (Improper Access Control)

## Which versions are affected by CVE-2021-28505?

It affects 1 product.


Products: Arista Eos.

## How do I fix CVE-2021-28505?

No fix has been published for CVE-2021-28505 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-28505 being exploited?

There is no known exploitation of CVE-2021-28505 in the wild and no public exploit code.

## Other vulnerabilities in Arista Networks EOS

- [CVE-2026-7473](https://insights.sbomify.com/CVE-2026-7473/): Arista Extensible Operating System Incomplete Comparison with Missing Factors (medium 6.9, exploited in the wild)
- [CVE-2015-8236](https://insights.sbomify.com/CVE-2015-8236/): Privilege escalation in n/a (critical 10.0)
- [CVE-2020-10188](https://insights.sbomify.com/CVE-2020-10188/): Memory corruption in n/a (critical 9.8)
- [CVE-2017-18017](https://insights.sbomify.com/CVE-2017-18017/): Use after free in n/a (critical 9.8)
- [CVE-2017-14491](https://insights.sbomify.com/CVE-2017-14491/): Memory corruption in n/a (critical 9.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-28505 and fix it if it is affected.

What it is: CVE-2021-28505 is a high-severity vulnerability in Arista Networks EOS, published on 14 Apr 2022. 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-2021-28505 in the wild and no public exploit code.

Affected product: Arista Networks EOS. 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-2021-28505/ (Markdown: https://insights.sbomify.com/CVE-2021-28505/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-28505
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-28505
- OSV: https://osv.dev/vulnerability/CVE-2021-28505

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-28505/
Summaries are generated and may contain mistakes; the official description above is the record.