# CVE-2026-21510: Microsoft Windows Shell Protection Mechanism Failure

> An unauthorized attacker can bypass a Windows Shell security feature over a network, requiring OS patches.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H/E:F/RL:O/RC:C`)
- **Exploited in the wild:** Yes, since 10 Feb 2026 (CISA KEV)
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** No
- **Published:** 10 Feb 2026
- **Updated:** 19 Aug 2026
- **Also known as:** GHSA-q6v4-4w5r-j7hr

## What is CVE-2026-21510?

CVE-2026-21510 is a high-severity vulnerability in Microsoft Windows 10 1607, published on 10 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

Protection mechanism failure in Windows Shell allows an unauthorized attacker to bypass a security feature over a network.

Weakness: CWE-693 (Protection Mechanism Failure)

## Which versions are affected by CVE-2026-21510?

It affects 13 products.


Products: Microsoft Windows 10 1607, Microsoft Windows 10 1809, Microsoft Windows 10 21h2, Microsoft Windows 10 22h2, Microsoft Windows 11 23h2, Microsoft Windows 11 24h2, Microsoft Windows 11 25h2, Microsoft Windows Server 2012, Microsoft Windows Server 2016, Microsoft Windows Server 2019, Microsoft Windows Server 2022, Microsoft Windows Server 2022 23h2, Microsoft Windows Server 2025.

## How do I fix CVE-2026-21510?

No fix has been published for CVE-2026-21510 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 3 Mar 2026.

## Is CVE-2026-21510 being exploited?

Yes. Attackers have exploited CVE-2026-21510 in the wild since at least 10 Feb 2026.

Public exploit code:

- CVE-2026-21510 (CVSS 8.8, Important) — Windows Shell security feature bypass. An attacker can trick a user into clicking a malicious link or shortcut file to bypass SmartScreen/Shell warnings and execute code without prompts. Publicly disclosed and exploited. (github_poc): https://github.com/andreassudo/CVE-2026-21510-CVSS-8.8-Important-Windows-Shell-security-feature-bypass
-  CVE-2026-21510 LNK generator PoC (github_poc): https://github.com/EpSiLoNPoInTOrI/EpSiLoNPoInTlnk

## Other vulnerabilities in Microsoft Windows 10 1607

- [CVE-2026-33824](https://insights.sbomify.com/CVE-2026-33824/): Microsoft Internet Key Exchange (IKE) Service Extensions Double Free (critical 9.8, exploited in the wild)
- [CVE-2026-21513](https://insights.sbomify.com/CVE-2026-21513/): Microsoft MSHTML Framework Protection Mechanism Failure (high 8.8, exploited in the wild)
- [CVE-2023-32049](https://insights.sbomify.com/CVE-2023-32049/): Microsoft Windows Defender SmartScreen Security Feature Bypass (high 8.8, exploited in the wild)
- [CVE-2023-29360](https://insights.sbomify.com/CVE-2023-29360/): Microsoft Streaming Service Untrusted Pointer Dereference (high 8.4, exploited in the wild)
- [CVE-2026-85880](https://insights.sbomify.com/CVE-2026-85880/): Microsoft Windows Heap-Based Buffer Overflow (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-21510 and fix it if it is affected.

What it is: CVE-2026-21510 is a high-severity vulnerability in Microsoft Windows 10 1607, published on 10 Feb 2026. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: Yes. Attackers have exploited CVE-2026-21510 in the wild since at least 10 Feb 2026.

Affected product: Microsoft Windows 10 1607. 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-2026-21510/ (Markdown: https://insights.sbomify.com/CVE-2026-21510/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-21510
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-21510
- OSV: https://osv.dev/vulnerability/CVE-2026-21510

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-21510/
Summaries are generated and may contain mistakes; the official description above is the record.