CVE-2026-3055: Citrix NetScaler Out-of-Bounds Read Vulnerability

In short

Citrix NetScaler has a weakness classified as out-of-bounds read (CWE-125). CISA added it to its Known Exploited Vulnerabilities catalog on 2026-03-30. NVD lists CVSS 4.0 at 9.3 CRITICAL.

What it is

“Citrix NetScaler ADC (formerly Citrix ADC), NetScaler Gateway (formerly Citrix Gateway) and NetScaler ADC FIPS and NDcPP contain an out-of-bounds reads vulnerability when configured as a SAML IDP leading to memory overread.” — CISA KEV, retrieved 2026-11-01

“Insufficient input validation in NetScaler ADC and NetScaler Gateway when configured as a SAML IDP leading to memory overread” — NVD, retrieved 2026-11-01

Who is affected

Citrix NetScaler. NVD lists the following versions as affected:

• Citrix Netscaler Application Delivery Controller: from 13.1 inclusive, before 13.1-37.262
• Citrix Netscaler Application Delivery Controller: from 13.1 inclusive, before 13.1-62.23
• Citrix Netscaler Application Delivery Controller: from 14.1 inclusive, before 14.1-60.58
• Citrix Netscaler Gateway: from 13.1 inclusive, before 13.1-62.23
• Citrix Netscaler Gateway: from 14.1 inclusive, before 14.1-60.58

Exploitation status

CISA KEV added: 2026-03-30. Known ransomware campaign use: Not reported by CISA. Due date CISA set for US federal civilian agencies: 2026-04-02.

Scores

NVD CVSS 4.0: 9.3 CRITICAL; vector CVSS:4.0/AV:N/AC:L/AT:N/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; source 50a63c94-1ea7-4568-8c11-eb79e7c5a2b5.

EPSS by FIRST: 91.49%; percentile 99.81; score date 2026-10-31. EPSS estimates the probability of exploitation in the next 30 days.

CWE: CWE-125.

Timeline

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 KEV

What to do

• Confirm whether you run Citrix NetScaler and which version.
• Apply the vendor update or mitigation in the advisory.
• Follow CISA’s required action.
• Review the vendor guidance on signs of compromise.
• Track the fix through completion.

References

• Vendor Advisory: https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX696300
• NVD detail
• CVE.org record
• CISA KEV catalog

Sources and dates

CISA Known Exploited Vulnerabilities Catalog, version 2026.10.30; retrieved 2026-11-01. CISA KEV data: CC0 1.0. No endorsement by CISA.

NVD retrieved: 2026-11-01. This product uses the NVD API but is not endorsed or certified by the NVD.

EPSS scores by FIRST; score date 2026-10-31.