# CVE-2023-4966: Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability

- Exploited (CISA KEV): yes, added 2023-10-18, known ransomware use
- Published: 2023-10-10
- CVSS: 9.4 CRITICAL (v3.1)
- EPSS: 100.0% (100th percentile)
- CWE: CWE-119

Sensitive information disclosure in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA  virtual server.

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

| Vendor | Status | First rule | Days after publication |
|---|---|---|---|
| Cloudflare | Blocks by default | 2025-07-21 | 650 |
| AWS | No public claim | — | — |
| Microsoft Azure | No public claim | — | — |
| Google Cloud | Before feed history | — | — |
| Fastly | Before feed history | — | — |
| F5 | Rule published | 2023-12-12 | 63 |
| Akamai | No public source | — | — |
| OWASP CRS | No public claim | — | — |

### Cloudflare

- 2025-07-21 · new · rule e012c7bece304a1daf80935ed1cf8e08 · default Block
  > Citrix Netscaler ADC - Information Disclosure - CVE:CVE-2023-4966. Previous action: Log. New action: Block. This is a New Detection
  Source: https://developers.cloudflare.com/changelog/post/2025-07-21-waf-release/

### F5

- 2023-12-12 · new · rule 200009292
  > Added: signature 200009292 "Citrix NetScaler Sensitive Information Disclosure" (Information Leakage, risk High), systems: Citrix. References: CVE-2023-4966.
  Source: https://docs.cloud.f5.com/docs-v2/platform/changelogs/security-details-changelog

## Our test (measured)

- OWASP Core Rule Set 4.25.0, paranoia level 1, anomaly threshold 5, default CRS settings: passed (0 of 2 requests blocked), template CVE-2023-4966, 2026-11-02
- OWASP Core Rule Set 4.25.0, paranoia level 2, anomaly threshold 5, default CRS settings: passed (0 of 2 requests blocked), template CVE-2023-4966, 2026-11-02

"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-2023-4966 · JSON: https://cve.vigilbase.com/api/v1/cves/CVE-2023-4966