# [CRIT] CISA KEV: CVE-2025-6543 — Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability

**Source:** CISA KEV
**Published:** 2025-06-30
**Article:** https://www.cisa.gov/known-exploited-vulnerabilities-catalog

## Threat Profile

CISA KEV entry. The U.S. federal "Known Exploited Vulnerabilities" catalog only adds CVEs that have been **observed exploited in the wild**. Federal civilian agencies are required to remediate by the published due date; the same prioritisation logic applies to any sensible enterprise SOC.

Vendor / Product: **Citrix NetScaler ADC and Gateway Buffer Overflow**

## Indicators of Compromise

- CVE-2025-6543 — match against your vulnerability scanner

## MITRE ATT&CK

- **T1190 — Exploit Public-Facing Application** (KEV implies active exploitation against exposed assets)

## Recommended hunts

Standard asset-exposure hunt — the canonical Splunk SPL and Defender KQL
live once in [`../_TEMPLATES.md#asset-exposure`](../_TEMPLATES.md#asset-exposure).
Substitute this CVE wherever the template references `<CVE>`:

- **CVE:** `CVE-2025-6543`

## Why this matters

Anything in CISA KEV is *currently* being exploited. Even if your scanners say "not vulnerable" because of patches, it's worth one quick check across your fleet — patch lag is the silent killer. Federal due-date dates also frequently match the timing your organisation will be asked about by auditors / regulators.

## Source body

Citrix NetScaler ADC and Gateway contain a buffer overflow vulnerability leading to unintended control flow and Denial of Service. NetScaler must be configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server. Vendor: Citrix, Product: NetScaler ADC and Gateway. Federal patch due: 2025-07-21. CVE-2025-6543