# CVE-2021-3523: Security feature bypass in apicast

> Attackers can bypass API security restrictions by exploiting connection reuse flaws when multiple APIs share an IP address.

- **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:** 27 Apr 2022
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-wxqh-rqgc-pfr9

## What is CVE-2021-3523?

CVE-2021-3523 is a high-severity vulnerability in apicast, published on 27 Apr 2022. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

A flaw was found in 3Scale APICast in versions prior to 2.11.0, where it incorrectly identified connections for reuse. This flaw allows an attacker to bypass security restrictions for an API request when hosting multiple APIs on the same IP address.

Weakness: CWE-281 (Improper Preservation of Permissions)

## Which versions are affected by CVE-2021-3523?

It affects 1 product.


Products: Redhat Apicast.

## How do I fix CVE-2021-3523?

No fix has been published for CVE-2021-3523 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-3523 being exploited?

There is no known exploitation of CVE-2021-3523 in the wild and no public exploit code.

## Other vulnerabilities in apicast

- [CVE-2023-0456](https://insights.sbomify.com/CVE-2023-0456/): Apicast proxies the api call with incorrect jwt token to the api backend without proper authorization check (high 7.4)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-3523 and fix it if it is affected.

What it is: CVE-2021-3523 is a high-severity vulnerability in apicast, published on 27 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-2021-3523 in the wild and no public exploit code.

Affected product: apicast. 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-2021-3523/ (Markdown: https://insights.sbomify.com/CVE-2021-3523/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-3523
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-3523
- OSV: https://osv.dev/vulnerability/CVE-2021-3523

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-3523/
Summaries are generated and may contain mistakes; the official description above is the record.