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Fencer Vulns
critical 9.8

CVE-2025-6543 kev in the critical feed json

Memory overflow vulnerability leading to unintended control flow and Denial of Service

published 2025-06-25 16 mo ago modified 2026-06-17 4 mo ago also EUVD-2025-19085

cvss
9.8
version 3.1, NVD
cisa kev
Exploited
added 2025-06-30
epss
10.4%
EPSS 10.4% chance of exploitation in 30 days, percentile 95%
public exploits
0
none known

Summary

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

Patch / fix

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.

  • NetScaler ADC 37.236, 47.46, 59.19
  • NetScaler Gateway 37.236, 47.46, 59.19

Timeline

  1. Published
  2. Added to CISA KEV
  3. CISA SSVC: exploitation active
  4. CISA patch deadline

Known exploited

Added
16 mo ago
Patch by
2025-07-21 (15 mo ago)
Ransomware
Not known
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.
Vendor, product
Citrix, NetScaler ADC and Gateway
CISA name
Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability

ATT&CK techniques

How it is exploited and what it leads to, in MITRE ATT&CK terms.

  • T1203 Exploitation for Client Execution exploitation
  • T1498 Network Denial of Service primary impact
  • T1059 Command and Scripting Interpreter secondary impact

kev release 2025-07-28, att&ck v16.1. KEV to ATT&CK mappings by the MITRE Center for Threat-Informed Defense (Mappings Explorer, Apache-2.0). © 2026 The MITRE Corporation. This work is reproduced and distributed with the permission of The MITRE Corporation. Terms of use

CISA SSVC

Exploitation
Active, exploited in the wild
Automatable
no
Technical impact
total
Assessed
15 mo ago

Exploit prediction

10.43% chance of exploitation in the next 30 days, higher than 95% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 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
CNA 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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Affected products

  • NetScaler ADC
  • NetScaler Gateway

Classification

Weakness
  • CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
Technology feeds

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.