# CVE-2021-34523: Microsoft Exchange Server Privilege Escalation Vulnerability

- Exploited (CISA KEV): yes, added 2021-11-03, known ransomware use
- Published: 2021-07-14
- CVSS: 9 CRITICAL (v3.1)
- EPSS: 100.0% (100th percentile)
- CWE: CWE-287

Microsoft Exchange Server Elevation of Privilege Vulnerability

## Edge WAF coverage (claimed by vendors, not measured)

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | Before feed history | — | — |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | Before feed history | — | — |
| Fastly | Before feed history | — | — |
| F5 | Rule published | 2024-01-16 | — |
| Akamai | No public source | — | — |
| OWASP CRS | Before feed history | — | — |

### F5

- 2024-01-16 · updated · rule 200018136
  > Updated: signature 200018136 "Microsoft Exchange ProxyShell Privilege Escalation" (Other Application Attacks, risk High), systems: Outlook Web Access. References: CVE-2021-34523.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog

"No public claim" means no vendor statement names this CVE; "Before feed history" means the CVE is older than the vendor feed. In both cases generic rules may still block it.

HTML: https://cve.vigilbase.com/cve/CVE-2021-34523 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2021-34523