# Citrix NetScaler ADC and Gateway: NetScaler ADC and Gateway Buffer Overflow Vulnerability · pwn.watch

> 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. Added to CISA KEV on 2025-06-30.

Page: https://pwn.watch/i/citrix-netscaler-adc-and-gateway-cve-2025-6543 · generated 2026-10-22T23:52:53.443Z

## Status
- Severity: critical · status: closed · patch: patched
- Product: Citrix NetScaler ADC and Gateway
- Started: 2025-06-30 · closed: 2025-06-30
- CVEs: CVE-2025-6543
- Affected: See vendor advisory / CISA notes (versions not always listed in KEV feed)
- Fixed in: See vendor advisory linked in sources

## Follow this incident
- RSS (one item per update): https://pwn.watch/i/citrix-netscaler-adc-and-gateway-cve-2025-6543/feed.xml
- JSON Feed: https://pwn.watch/i/citrix-netscaler-adc-and-gateway-cve-2025-6543/feed.json
- Full data (timeline, sources, posts, agentBrief): https://pwn.watch/i/citrix-netscaler-adc-and-gateway-cve-2025-6543.json
- This file: https://pwn.watch/i/citrix-netscaler-adc-and-gateway-cve-2025-6543/llms.txt

## Updates (newest first)
- 2025-06-30: CISA added CVE-2025-6543 to the KEV catalog (due 2025-07-21).

## Fix brief
# Security brief: Citrix NetScaler ADC and Gateway: NetScaler ADC and Gateway Buffer Overflow Vulnerability

Source: https://pwn.watch/i/citrix-netscaler-adc-and-gateway-cve-2025-6543 · status: closed (closed Jun 30, 2025) · severity: critical · updated Jun 30, 2025

## Patch status
**PATCHED: fixed releases exist. Upgrade to a fixed version.**

## What it is
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. Added to CISA KEV on 2025-06-30.

Severity detail: CVSS 9.2 (CNA, v4.0); actively exploited (CISA KEV)

- Product: Citrix NetScaler ADC and Gateway
- CVE / advisory ids: CVE-2025-6543

## Affected versions
- See vendor advisory / CISA notes (versions not always listed in KEV feed)

## Check whether you're affected
No generic command applies (the product is a hosted service, appliance or desktop app). Check the installed version in its admin UI / About screen and compare with the versions above.

## Fix
Upgrade to one of these fixed versions (or later on the same branch):
- See vendor advisory linked in sources

After upgrading, re-run the checks above and redeploy/restart the affected services.

## Latest updates
- Jun 30, 2025: CISA added CVE-2025-6543 to the KEV catalog (due 2025-07-21).

## Advisories
- [Citrix advisory: Citrix NetScaler ADC and Gateway](https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX694788) (Citrix)
- [Citrix advisory: Citrix NetScaler ADC and Gateway](https://www.netscaler.com/blog/news/netscaler-critical-security-updates-for-cve-2025-6543-and-cve-2025-5777/) (Citrix)
- [NVD: CVE-2025-6543](https://nvd.nist.gov/vuln/detail/CVE-2025-6543) (NVD)
- [CISA Known Exploited Vulnerabilities Catalog](https://www.cisa.gov/known-exploited-vulnerabilities-catalog) (CISA)

## Caveats
Derived from CISA KEV JSON feed catalogVersion 2026.10.21. CVSS from the CVE record (cvelistV5). Exact affected/fixed version strings are not always in the KEV record; verify against the vendor advisory URL. startedAt uses dateAdded (exploitation may have begun earlier; many entries are older CVEs newly confirmed as exploited in 2025).

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Machine-readable: https://pwn.watch/i/citrix-netscaler-adc-and-gateway-cve-2025-6543.json · all incidents: https://pwn.watch/incidents.json. Verify against the vendor advisory before changing production systems.