# CVE-2026-41091: Microsoft Defender Link Following

> An authorized local attacker can elevate privileges by exploiting improper link resolution in Microsoft Defender.

- **Severity:** High 7.8 (`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`)
- **Exploited in the wild:** Yes, since 20 May 2026 (CISA KEV)
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 20 May 2026
- **Updated:** 10 Aug 2026
- **Also known as:** GHSA-h776-j9jw-992p

## What is CVE-2026-41091?

CVE-2026-41091 is a high-severity path traversal vulnerability in Microsoft Malware Protection Engine, published on 20 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Improper link resolution before file access ('link following') in Microsoft Defender allows an authorized attacker to elevate privileges locally.

Weakness: CWE-59 (Improper Link Resolution Before File Access)

## Which versions are affected by CVE-2026-41091?

It affects 1 product.


Products: Microsoft Malware Protection Engine.

## How do I fix CVE-2026-41091?

No fix has been published for CVE-2026-41091 yet. Limit exposure of the affected software until one is available. US federal agencies must fix it by 3 Jun 2026.

## Is CVE-2026-41091 being exploited?

Yes. Attackers have exploited CVE-2026-41091 in the wild since at least 20 May 2026.

Public exploit code:

- CVE-2026-41091 (github_poc): https://github.com/0xredash/CVE-2026-41091
- CVE-2026-41091 RedSun | Microsoft Defender LPE exploit. Low-privileged users gain NT AUTHORITY\SYSTEM - via Cloud Files API + NTFS junction trickery. Forces Defender to write malicious payloads to System32 with SYSTEM rights - Actively exploited in wild. CVSS 7.8. Patch: Defender Engine 1.1.26040.8. Educational & Legal uses only. (github_poc): https://github.com/tc4dy/CVE-2026-41091-PoC-Exploit
- Windwos Zero Day Local PrivESc Exploit (CVE-2026-41091) (github_poc): https://github.com/s4m98/RedSun-
- Scanner: CVE-2026-41091/45498 Microsoft Defender LPE/DoS — Python scanner for Windows Defender privilege escalation (CISA KEV) (github_poc): https://github.com/ridhinva/defender-privilege-escalation-scanner

## Other vulnerabilities in Microsoft Malware Protection Engine

- [CVE-2013-1346](https://insights.sbomify.com/CVE-2013-1346/): Memory corruption in n/a (critical 9.3)
- [CVE-2026-45584](https://insights.sbomify.com/CVE-2026-45584/): Microsoft Defender Remote Code Execution Vulnerability (high 8.1)
- [CVE-2026-69414](https://insights.sbomify.com/CVE-2026-69414/): Microsoft Defender Elevation of Privilege Vulnerability (high 7.8)
- [CVE-2026-55011](https://insights.sbomify.com/CVE-2026-55011/): Microsoft Defender Remote Code Execution Vulnerability (high 7.8)
- [CVE-2026-55012](https://insights.sbomify.com/CVE-2026-55012/): Microsoft Defender Remote Code Execution Vulnerability (high 7.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-41091 and fix it if it is affected.

What it is: CVE-2026-41091 is a high-severity path traversal vulnerability in Microsoft Malware Protection Engine, published on 20 May 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: Yes. Attackers have exploited CVE-2026-41091 in the wild since at least 20 May 2026.

Affected product: Microsoft Malware Protection Engine. 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-2026-41091/ (Markdown: https://insights.sbomify.com/CVE-2026-41091/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-41091
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-41091
- OSV: https://osv.dev/vulnerability/CVE-2026-41091

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-41091/
Summaries are generated and may contain mistakes; the official description above is the record.