# CVE-2021-28504: Security feature bypass in EOS

> Attackers can bypass IPv4 access-list rules on Arista Strata devices when TCAM profile is enabled and VXLAN protocol is matched.

- **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:** 1 Apr 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-2pcc-vj7h-7frv

## What is CVE-2021-28504?

CVE-2021-28504 is a high-severity vulnerability in Arista Networks EOS, published on 1 Apr 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

On Arista Strata family products which have “TCAM profile” feature enabled when Port IPv4 access-list has a rule which matches on “vxlan” as protocol then that rule and subsequent rules ( rules declared after it in ACL ) do not match on IP protocol field as expected.

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

## Which versions are affected by CVE-2021-28504?

It affects 1 product.


Products: Arista Eos.

## How do I fix CVE-2021-28504?

No fix has been published for CVE-2021-28504 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-28504 being exploited?

There is no known exploitation of CVE-2021-28504 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-2021-28504 and fix it if it is affected.

What it is: CVE-2021-28504 is a high-severity vulnerability in Arista Networks EOS, published on 1 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-2021-28504 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-2021-28504/ (Markdown: https://insights.sbomify.com/CVE-2021-28504/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-28504
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-28504
- OSV: https://osv.dev/vulnerability/CVE-2021-28504

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-28504/
Summaries are generated and may contain mistakes; the official description above is the record.