# CVE-2021-22976: Denial of service in BIG-IP Advanced WAF & BIG-IP ASM

> Attackers can cause excessive CPU usage and denial of service by sending WebSocket requests with unusually large JSON payloads to BIG-IP ASM.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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:** 12 Feb 2021
- **Updated:** 3 Aug 2024
- **Also known as:** GHSA-5m63-vxpq-9j8m

## What is CVE-2021-22976?

CVE-2021-22976 is a high-severity denial of service vulnerability in F5 Big-Ip Advanced Web Application Firewall, published on 12 Feb 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

On BIG-IP Advanced WAF and ASM version 16.0.x before 16.0.1.1, 15.1.x before 15.1.2, 14.1.x before 14.1.3.1, 13.1.x before 13.1.3.6, and all 12.1.x versions, when the BIG-IP ASM system processes WebSocket requests with JSON payloads, an unusually large number of parameters can cause excessive CPU usage in the BIG-IP ASM bd process. Note: Software versions which have reached End of Software Development (EoSD) are not evaluated.

## Which versions are affected by CVE-2021-22976?

It affects 2 products.


Products: F5 Big-Ip Advanced Web Application Firewall, F5 Big-Ip Application Security Manager.

## How do I fix CVE-2021-22976?

No fix has been published for CVE-2021-22976 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-22976 being exploited?

There is no known exploitation of CVE-2021-22976 in the wild and no public exploit code.

## Other vulnerabilities in F5 Big-Ip Advanced Web Application Firewall

- [CVE-2021-23031](https://insights.sbomify.com/CVE-2021-23031/): Privilege escalation in BIG-IP Advanced WAF and BIG-IP ASM (critical 9.9)
- [CVE-2021-23029](https://insights.sbomify.com/CVE-2021-23029/): Server-side request forgery in BIG-IP Advanced WAF and BIG-IP ASM (high 8.8)
- [CVE-2021-23014](https://insights.sbomify.com/CVE-2021-23014/): Missing authorization in BIG-IP ASM/Advanced WAF (high 8.8)
- [CVE-2021-22993](https://insights.sbomify.com/CVE-2021-22993/): Cross-site scripting in BIG-IP Advanced WAF and BIG-IP ASM (high 8.8)
- [CVE-2026-40060](https://insights.sbomify.com/CVE-2026-40060/): BIG-IP Advanced WAF and ASM vulnerability (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-22976 and fix it if it is affected.

What it is: CVE-2021-22976 is a high-severity denial of service vulnerability in F5 Big-Ip Advanced Web Application Firewall, published on 12 Feb 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-2021-22976 in the wild and no public exploit code.

Affected product: F5 Big-Ip Advanced Web Application Firewall. 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-2021-22976/ (Markdown: https://insights.sbomify.com/CVE-2021-22976/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-22976
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-22976
- OSV: https://osv.dev/vulnerability/CVE-2021-22976

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-22976/
Summaries are generated and may contain mistakes; the official description above is the record.