# CVE-2021-0262: Junos OS: QFX10002-60C: Use after free vulnerability found during static code analysis

> A use-after-free flaw in Junos OS packet processing allows adjacent attackers to cause a persistent denial of service on QFX10002-60C switches.

- **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:** 22 Apr 2021
- **Updated:** 17 Sep 2024
- **Also known as:** GHSA-8h37-v9pc-m6v6

## What is CVE-2021-0262?

CVE-2021-0262 is a medium-severity use after free vulnerability in Juniper Junos, 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

Through routine static code analysis of the Juniper Networks Junos OS software codebase, the Secure Development Life Cycle team identified a Use After Free vulnerability in PFE packet processing on the QFX10002-60C switching platform. Exploitation of this vulnerability may allow a logically adjacent attacker to trigger a Denial of Service (DoS). Continued exploitation of this vulnerability will sustain the Denial of Service (DoS) condition. This issue only affects QFX10002-60C devices. No other product or platform is vulnerable to this issue. This issue affects Juniper Networks Junos OS on QFX10002-60C: 19.1 version 19.1R3-S1 and later versions; 19.1 versions prior to 19.1R3-S3; 19.2 version 19.2R2 and later versions; 19.2 versions prior to 19.2R3-S1; 20.2 versions prior to 20.2R1-S2. This issue does not affect Juniper Networks Junos OS: versions prior to 19.1R3; 19.2 versions prior to 19.2R2; any version of 19.3; version 20.2R2 and later releases.

Weakness: CWE-416 (Use After Free)

## Which versions are affected by CVE-2021-0262?

It affects 1 product.


Products: Juniper Junos.

## How do I fix CVE-2021-0262?

No fix has been published for CVE-2021-0262 yet. Limit exposure of the affected software until one is available.

## Is CVE-2021-0262 being exploited?

There is no known exploitation of CVE-2021-0262 in the wild and no public exploit code.

## Other vulnerabilities in Juniper Junos

- [CVE-2023-36845](https://insights.sbomify.com/CVE-2023-36845/): Juniper Junos OS EX Series and SRX Series PHP External Variable Modification (critical 9.8, exploited in the wild)
- [CVE-2020-1631](https://insights.sbomify.com/CVE-2020-1631/): Juniper Junos OS Path Traversal (high 8.8, exploited in the wild)
- [CVE-2025-21590](https://insights.sbomify.com/CVE-2025-21590/): Juniper Junos OS Improper Isolation or Compartmentalization (medium 6.7, exploited in the wild)
- [CVE-2023-36851](https://insights.sbomify.com/CVE-2023-36851/): Juniper Junos OS SRX Series Missing Authentication for Critical Function (medium 5.3, exploited in the wild)
- [CVE-2023-36844](https://insights.sbomify.com/CVE-2023-36844/): Juniper Junos OS EX Series PHP External Variable Modification (medium 5.3, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-0262 and fix it if it is affected.

What it is: CVE-2021-0262 is a medium-severity use after free vulnerability in Juniper Junos, 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-2021-0262 in the wild and no public exploit code.

Affected product: Juniper Junos. 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-2021-0262/ (Markdown: https://insights.sbomify.com/CVE-2021-0262/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-0262
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-0262
- OSV: https://osv.dev/vulnerability/CVE-2021-0262

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-0262/
Summaries are generated and may contain mistakes; the official description above is the record.