# CVE-2021-27562: Arm Trusted Firmware Out-of-Bounds Write Vulnerability

- Exploited (CISA KEV): yes, added 2021-11-03
- Published: 2021-05-25
- CVSS: 5.5 MEDIUM (v3.1)
- EPSS: 3.1% (88th percentile)
- CWE: CWE-787

In Arm Trusted Firmware M through 1.2, the NS world may trigger a system halt, an overwrite of secure data, or the printing out of secure data when calling secure functions under the NSPE handler mode.

## 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 | Before feed history | — | — |
| Akamai | No public source | — | — |
| OWASP CRS | Before feed history | — | — |

"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.

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