# CVE-2026-21537: Microsoft Defender for Endpoint Linux Extension Remote Code Execution Vulnerability

> An unauthorized attacker can execute code over an adjacent network due to improper code generation in Microsoft Defender for Endpoint Linux.

- **Severity:** High 8.8 (`CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`)
- **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:** 10 Feb 2026
- **Updated:** 19 Aug 2026
- **Also known as:** GHSA-c8x6-p29h-wm35

## What is CVE-2026-21537?

CVE-2026-21537 is a high-severity code injection vulnerability in Microsoft Defender for Endpoint for Linux, published on 10 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Improper control of generation of code ('code injection') in Microsoft Defender for Linux allows an unauthorized attacker to execute code over an adjacent network.

Weakness: CWE-94 (Improper Control of Generation of Code)

## Which versions are affected by CVE-2026-21537?

It affects 1 product.


Products: Microsoft Defender for Endpoint.

## How do I fix CVE-2026-21537?

No fix has been published for CVE-2026-21537 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-21537 being exploited?

There is no known exploitation of CVE-2026-21537 in the wild and no public exploit code.

## Other vulnerabilities in Microsoft Defender for Endpoint for Linux

- [CVE-2024-49057](https://insights.sbomify.com/CVE-2024-49057/): Microsoft Defender for Endpoint on Android Spoofing Vulnerability (high 8.1)
- [CVE-2025-47161](https://insights.sbomify.com/CVE-2025-47161/): Microsoft Defender for Endpoint Elevation of Privilege Vulnerability (high 7.8)
- [CVE-2024-21315](https://insights.sbomify.com/CVE-2024-21315/): Microsoft Defender for Endpoint Protection Elevation of Privilege Vulnerability (high 7.8)
- [CVE-2022-35828](https://insights.sbomify.com/CVE-2022-35828/): Microsoft Defender for Endpoint for Mac Elevation of Privilege Vulnerability (high 7.8)
- [CVE-2026-50658](https://insights.sbomify.com/CVE-2026-50658/): Microsoft Defender for Endpoint for Mac Elevation of Privilege Vulnerability (high 7.0)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-21537 and fix it if it is affected.

What it is: CVE-2026-21537 is a high-severity code injection vulnerability in Microsoft Defender for Endpoint for Linux, published on 10 Feb 2026. 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-2026-21537 in the wild and no public exploit code.

Affected product: Microsoft Defender for Endpoint for Linux. 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-2026-21537/ (Markdown: https://insights.sbomify.com/CVE-2026-21537/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-21537
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-21537
- OSV: https://osv.dev/vulnerability/CVE-2026-21537

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-21537/
Summaries are generated and may contain mistakes; the official description above is the record.