# CVE-2021-0226: Junos OS Evolved: The IPv6 BGP session will flap due to receipt of a specific IPv6 packet

> Attackers can cause IPv6 BGP session termination and sustained denial of service on Juniper Junos OS Evolved devices by sending specific IPv6 packets.

- **Severity:** High 7.1 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 22 Apr 2021
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-7jmp-9phw-35g8

## What is CVE-2021-0226?

CVE-2021-0226 is a high-severity denial of service vulnerability in Juniper Junos Os Evolved, published on 22 Apr 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

On Juniper Networks Junos OS Evolved devices, receipt of a specific IPv6 packet may cause an established IPv6 BGP session to terminate, creating a Denial of Service (DoS) condition. Continued receipt and processing of this packet will create a sustained Denial of Service (DoS) condition. This issue does not affect IPv4 BGP sessions. This issue affects IBGP or EBGP peer sessions with IPv6. This issue affects: Juniper Networks Junos OS Evolved: 19.4 versions prior to 19.4R2-S3-EVO; 20.1 versions prior to 20.1R2-S3-EVO; 20.2 versions prior to 20.2R2-S1-EVO; 20.3 versions prior to 20.3R2-EVO. This issue does not affect Juniper Networks Junos OS releases.

Weakness: CWE-665 (Improper Initialization)

## Which versions are affected by CVE-2021-0226?

It affects 1 product.


Products: Juniper Junos Os Evolved.

## How do I fix CVE-2021-0226?

No fix has been published for CVE-2021-0226 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-0226 being exploited?

There is no known exploitation of CVE-2021-0226 in the wild and no public exploit code.

## Other vulnerabilities in Juniper Junos Os Evolved

- [CVE-2026-21902](https://insights.sbomify.com/CVE-2026-21902/): Junos OS Evolved: PTX Series: A vulnerability allows a unauthenticated, network-based attacker to execute code as root (critical 9.3)
- [CVE-2023-28983](https://insights.sbomify.com/CVE-2023-28983/): Junos OS Evolved: Shell Injection vulnerability in the gNOI server (high 8.8)
- [CVE-2025-21599](https://insights.sbomify.com/CVE-2025-21599/): Denial of service in Junos OS Evolved (high 8.7)
- [CVE-2024-47502](https://insights.sbomify.com/CVE-2024-47502/): Junos OS Evolved: TCP session state is not always cleared on the Routing Engine leading to DoS (high 8.7)
- [CVE-2024-39531](https://insights.sbomify.com/CVE-2024-39531/): Junos OS Evolved: ACX 7000 Series: Protocol specific DDoS configuration affects other protocols (high 8.7)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-0226 and fix it if it is affected.

What it is: CVE-2021-0226 is a high-severity denial of service vulnerability in Juniper Junos Os Evolved, published on 22 Apr 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2021-0226 in the wild and no public exploit code.

Affected product: Juniper Junos Os Evolved. 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-2021-0226/ (Markdown: https://insights.sbomify.com/CVE-2021-0226/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-0226
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-0226
- OSV: https://osv.dev/vulnerability/CVE-2021-0226

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From sbomify Insights: https://insights.sbomify.com/CVE-2021-0226/
Summaries are generated and may contain mistakes; the official description above is the record.