---
cve: "CVE-2021-31207"
severity: "MEDIUM"
cvss: 6.6
epss: "99.8%"
vendor: "Microsoft"
kev: true
exploited: true
published: "2021-05-11 19:15:10"
tags: [cve, security, medium]
source: tsecurity.de CVE-Dossier
exported: "2026-11-09T15:04:09+01:00"
---

# CVE-2021-31207

> 6.6 MEDIUM · ⚠️ CISA KEV (1832 Tage) · 🔓 Exploited · 🧪 PoC

## Beschreibung

Microsoft Exchange Server Security Feature Bypass Vulnerability

## CNA-Record (Kanon, cvelistV5)

- CNA: **microsoft**
- State: PUBLISHED
- Stand: 2025-10-21 23:25:45
- CNA-CVSS: **6.6** (`CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C`)

## CISA-Anreicherung (vulnrichment/ADP)

- CISA KEV seit: **03.11.2021**
- CISA-SSVC (Coordinator, v2.0.3):
  - Exploitation: **active**
  - Automatable: **no**
  - Technical Impact: **total**

## CVSS-Vektor

```
CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:H/I:H/A:H/E:U/RL:O/RC:C
```

| Metrik | Wert | Bewertung |
|---|---|---|
| AV Angriffsvektor | Netzwerk | bad |
| AC Komplexität | Hoch | good |
| PR Privilegien | Hoch | good |
| UI Interaktion | Keine | bad |
| S Scope | Unverändert | good |
| C Vertraulichkeit | Hoch | bad |
| I Integrität | Hoch | bad |
| A Verfügbarkeit | Hoch | bad |

## Schwachstellen-Klasse

- **CWE-434** — Unrestricted Upload of File with Dangerous Type
  The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.

## Angriffsmuster (CAPEC)

- [CAPEC-1 — Accessing Functionality Not Properly Constrained by ACLs](https://capec.mitre.org/data/definitions/1.html) _(Severity: High)_

## ATT&CK-Techniken

- [T1574.010 — Hijack Execution Flow: ServicesFile Permissions Weakness](https://attack.mitre.org/techniques/T1574/010/)

## Referenzen

- <https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2021-31207>
- <https://www.zerodayinitiative.com/advisories/ZDI-21-819/>
- <http://packetstormsecurity.com/files/163895/Microsoft-Exchange-ProxyShell-Remote-Code-Execution.html>
- <https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-31207>

---
_Exportiert aus dem [tsecurity.de CVE-Dossier](https://tsecurity.de/sicherheitsluecken/cve-2021-31207/) · Datenquellen: EUVD (ENISA), NVD, OSV, CISA KEV, FIRST EPSS, Exploit-DB, BSI WID (CSAF)_