---
title: "CVE-2025-6543: Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability"
url: https://erroneo.us/security/cve/CVE-2025-6543/
description: "CVE-2025-6543 (Citrix NetScaler ADC and Gateway): Exploited in the wild (CISA KEV). Memory overflow vulnerability leading to unintended control flow and…"
type: vulnerability-record
section: "Security Digest"
date_published: 2025-06-25
date_modified: 2026-10-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2025-6543"
kev: true
cvss: 9.2
epss: 0.10562
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2025-6543: Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability

**Signal:** Exploited: patch now if you run it. CISA has confirmed exploitation in the wild. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- Yes, if you run Citrix NetScaler ADC and Gateway. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2025-06-30, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2025-07-21 ; treat that as the outer limit, not the target.
- EPSS 10.6% , percentile 96: FIRST’s model estimates a 10.6% chance of exploitation activity in the next 30 days, higher than 96% of all scored CVEs (very high). EPSS is a probability, not a verdict.
- Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
- Editorial verdict: Check exposure. Citrix Bleed 2: NetScaler Gateway Memory Leak — A pre-auth memory leak on internet-facing VPN gateways that was exploited within weeks; patched since June 2025, so the job now is proving you patched, killed sessions and were not session-hijacked.

## What it is

Memory overflow vulnerability leading to unintended control flow and Denial of Service in NetScaler ADC and NetScaler Gateway when configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) OR AAA virtual server

## Affected products (CVE record)

- NetScaler ADC: 14.1 < 47.46, 13.1 < 59.19, 13.1 FIPS and NDcPP < 37.236
- NetScaler Gateway: 14.1 < 47.46, 13.1 < 59.19, 13.1 FIPS and NDcPP < 37.236

## Severity

- Citrix CVSS 4.0: 9.2 `CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:L/SI:L/SA:L`

## Exploitation

- CISA KEV: added 2025-06-30; federal due date 2025-07-21. Known ransomware use: Unknown.
- CISA required action: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.
- CISA SSVC assessment: exploitation active , automatable no , technical impact total .
- FIRST EPSS (model of 2026-10-21): 10.56% probability of exploitation activity in the next 30 days; percentile 96.

## Sources

- [Listed in CISA KEV notes (support.citrix.com)](https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX694788)
- [Listed in CISA KEV notes (netscaler.com)](https://www.netscaler.com/blog/news/netscaler-critical-security-updates-for-cve-2025-6543-and-cve-2025-5777/)
- [CVE.org record CVE-2025-6543](https://www.cve.org/CVERecord?id=CVE-2025-6543)
- [NVD entry CVE-2025-6543](https://nvd.nist.gov/vuln/detail/CVE-2025-6543)
- [CISA Known Exploited Vulnerabilities catalog entry](https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2025-6543)

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Source page: https://erroneo.us/security/cve/CVE-2025-6543/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt