Citrix NetScaler ADC and Gateway Buffer Overflow Vulnerability

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

CheckOps priority index

6.4/10 Patch within 7 days

Severity9.2

Probability1.0

Exploitation4/5

Severity = CVSS. Probability = EPSS (FIRST). Exploitation = public signals: KEV, EUVD, ransomware, EPSS above 10 %, no account required.

EPSS · today 10.4% higher than 95.7% of CVEs

CVSS 4.0 9.2 AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/

Exploited for 491 days 30 Jun 2025

CISA due date 21 Jul 2025 for US federal agencies

Exploitation probability EPSS · FIRST

EPSS probability (%)Percentile among all CVEs

Exploitation signals 4 / 5

KEV catalog (CISA)30 Jun 2025
Exploited in EUVD (ENISA)30 Jun 2025
Used by ransomwareno
EPSS above 10 %10.4%
No account, over the networkyes

What to do

Fix

Apply the vendor’s fix as soon as it is available.

CISA guidance: Apply mitigations per vendor instructions, follow applicable BOD 22-01 guidance for cloud services, or discontinue use of the product if mitigations are unavailable.

Meanwhile

Take the service off the internet or restrict access to it, watch the logs and look for signs of compromise.

Manufacturers (CRA)

Exploited vulnerability in your product: early warning to ENISA within 24 h, then notification within 72 h (Article 14 of the Cyber Resilience Act). The CRA explained

Affected products

ADCGatewayNetScaler ADC and Gateway

Affected versions

13.1 FIPS and NDcPP <37.236
14.1 <47.46
13.1 <59.19

Weaknesses (CWE)

CWE-119

Open source packages OSV

Affected libraries according to OSV, with fixed versions.

Timeline

25 Jun 2025
Published
30 Jun 2025
Exploitation reported (ENISA)
30 Jun 2025
Added to the KEV catalog
21 Jul 2025
CISA remediation due date
26 Sept 2026
EPSS peak: 10.6%

References

Other exploited vulnerabilities from the same vendor

CVE-2026-88779Citrix NetScaler Improper Restriction of Operations within the Bounds of a Memory Buffer Vulnerability
6.2 · Actively exploited
CVE-2026-88772Citrix NetScaler Improper Restriction of Operations within the Bounds of a Memory Buffer Vulnerability
8.5 · Actively exploited
CVE-2026-88771Citrix NetScaler Improper Input Validation Vulnerability
8.7 · Actively exploited
CVE-2026-19490Citrix NetScaler Authentication Bypass Using an Alternate Path or Channel Vulnerability
7.1 · Actively exploited
CVE-2026-8452Citrix NetScaler ADC and NetScaler Gateway Improper Restriction of Operations within the Bounds of a Memory Buffer Vulnerability
5.4 · Actively exploited
CVE-2026-3055Citrix NetScaler Out-of-Bounds Read Vulnerability
8.9 · Background exploitation