# CVE-2021-0209: Junos OS Evolved: Receipt of certain valid BGP update packets from BGP peers may cause RPD to core when using REGEX.

> An attacker can cause a denial of service in Junos OS Evolved by sending specific BGP packets when REGEX is used, crashing the routing process.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:A/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:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Jan 2021
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-gp8q-5m2c-vprm

## What is CVE-2021-0209?

CVE-2021-0209 is a medium-severity vulnerability in Juniper Junos Os Evolved, published on 15 Jan 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

In Juniper Networks Junos OS Evolved an attacker sending certain valid BGP update packets may cause Junos OS Evolved to access an uninitialized pointer causing RPD to core leading to a Denial of Service (DoS). Continued receipt of these types of valid BGP update packets will cause an extended Denial of Service condition. RPD will require a restart to recover. An indicator of compromise is to see if the file rpd.re exists by issuing the command: show system core-dumps This issue affects: Juniper Networks Junos OS Evolved 19.4 versions prior to 19.4R2-S2-EVO; 20.1 versions prior to 20.1R1-S2-EVO, 20.1R2-S1-EVO. This issue does not affect Junos OS.

Weakness: CWE-824 (Access of Uninitialized Pointer)

## Which versions are affected by CVE-2021-0209?

It affects 1 product.


Products: Juniper Junos Os Evolved.

## How do I fix CVE-2021-0209?

No fix has been published for CVE-2021-0209 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-0209 being exploited?

There is no known exploitation of CVE-2021-0209 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-2021-0209 and fix it if it is affected.

What it is: CVE-2021-0209 is a medium-severity vulnerability in Juniper Junos Os Evolved, published on 15 Jan 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-2021-0209 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-2021-0209/ (Markdown: https://insights.sbomify.com/CVE-2021-0209/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-0209
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-0209
- OSV: https://osv.dev/vulnerability/CVE-2021-0209

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-0209/
Summaries are generated and may contain mistakes; the official description above is the record.