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CVE-2026-88777 – Denial of Service (Memory Overflow) – Citrix NetScaler ADC and NetScaler Gateway 14

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Summary

CVE-2026-88777 is a memory overflow vulnerability affecting Citrix NetScaler ADC and NetScaler Gateway. On appliances configured as a load balancing (LB) or content switching (CS) virtual server, or as a CGNAT (LSN/NAT64) device, with a non-HTTP Layer 7 feature such as FTP, RTSP, or DNS64 enabled, an unauthenticated network attacker can trigger unpredictable or erroneous behavior or a Denial of Service. It carries a CVSS v3.1 base score of 8.8 (High) and was published on September 27, 2026 as part of Citrix’s broader NetScaler security bulletin.

Technical details

  • Root cause: A memory overflow condition in NetScaler’s handling of non-HTTP Layer 7 protocol processing on LB/CS or CGNAT-LSN/NAT64 configurations.
  • Trigger conditions: The affected appliance must have a load balancing or content switching virtual server, or CGNAT-LSN/NAT64 functionality, configured with a non-HTTP Layer 7 feature enabled (e.g., FTP, RTSP, or DNS64).
  • Attack vector: Network — no authentication and no user interaction is required to exploit the flaw.
  • Impact: Unpredictable/erroneous device behavior or Denial of Service; the vulnerability does not itself grant code execution.

Affected software

  • Citrix NetScaler ADC before 14.1-73.37
  • Citrix NetScaler ADC before 13.1-64.23
  • Citrix NetScaler ADC 14.1-73.37 FIPS and NDcPP builds (fixed release required)
  • Citrix NetScaler ADC before 13.1-37.279 FIPS and NDcPP
  • Citrix NetScaler Gateway before 14.1-73.37
  • Citrix NetScaler Gateway before 13.1-64.23

Severity

  • CVSS v3.1 Base Score: 8.8 (High)
  • Note: Citrix’s published advisory scores this vulnerability using CVSS v4.0 (8.8, Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:H/SC:N/SI:N/SA:N); no separate CVSS v3.1 vector has been published by the vendor at this time.

Mitigation and recommended actions

  • Immediate: Upgrade to a fixed build:
    • NetScaler ADC and Gateway 14.1-73.37 or later
    • NetScaler ADC and Gateway 13.1-64.23 or later
    • NetScaler ADC 13.1-37.279 or later for FIPS and NDcPP deployments
  • If patching cannot be applied immediately: Review configurations for LB/CS virtual servers or CGNAT-LSN/NAT64 features with non-HTTP Layer 7 protocols (FTP, RTSP, DNS64) enabled, and restrict or disable these features where not operationally required until the upgrade can be completed. Configuration changes should be treated as a temporary risk-reduction step, not a substitute for patching.

References

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