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CVE-2026-88772 – Remote Code Execution / Denial of Service – Citrix NetScaler ADC and Gateway (DTLS)

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Summary

CVE-2026-88772 is a memory overflow vulnerability in Citrix NetScaler ADC and NetScaler Gateway that can lead to remote code execution or denial of service on appliances with DTLS enabled. Citrix has confirmed the flaw is being actively exploited in the wild against unmitigated deployments, and rates it critical. Because DTLS is enabled by default on VPN virtual servers, most NetScaler Gateway configurations are exposed unless DTLS has been explicitly turned off.

Technical details

  • Root cause: A memory overflow condition in NetScaler’s handling of DTLS traffic.
  • Trigger condition: The appliance must have DTLS configured/enabled; DTLS is on by default for VPN virtual servers unless an administrator has explicitly disabled it.
  • Attack vector: Network-based, requiring no authentication from the attacker.
  • Impact: Successful exploitation can result in remote code execution or denial of service on the affected appliance.
  • Exploitation status: Citrix has stated that exploitation of this vulnerability on unmitigated NetScaler deployments has been observed in the wild, alongside the companion vulnerability CVE-2026-88771.
  • Citrix has not disclosed further technical details, indicators of compromise, or attacker identities.

Affected software

  • Citrix NetScaler ADC and NetScaler Gateway 14.1 before 14.1-73.37
  • Citrix NetScaler ADC and NetScaler Gateway 13.1 before 13.1-64.23
  • Citrix NetScaler ADC 14.1-FIPS before 14.1-73.37 FIPS
  • Citrix NetScaler ADC 13.1-FIPS and 13.1-NDcPP before 13.1-37.279

Severity

  • CVSS v4.0 Base Score: 9.5 (Critical)
  • Vector: CVSS:4.0/AV:N/AC:H/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H

Mitigation and recommended actions

  • Immediate: Upgrade to a patched build as soon as possible:
    • NetScaler ADC and NetScaler Gateway 14.1-73.37 or later
    • NetScaler ADC and NetScaler Gateway 13.1-64.23 or later
    • NetScaler ADC 14.1-FIPS 14.1-73.37 FIPS or later
    • NetScaler ADC 13.1-FIPS and 13.1-NDcPP 13.1-37.279 or later
  • If patching cannot be completed immediately: Citrix has not published a workaround for this vulnerability; where possible, disable DTLS on VPN virtual servers as an interim risk-reduction step and restrict/monitor network access to internet-facing NetScaler management and gateway interfaces until the patch is applied. Given confirmed active exploitation, treat patching as urgent.

References

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