CVE-2025-7776 Overview
CVE-2025-7776 is a memory overflow vulnerability in Citrix NetScaler Application Delivery Controller (ADC) and NetScaler Gateway. The flaw triggers when the appliance is configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, or RDP Proxy) with a PCoIP Profile bound to it. Unauthenticated network attackers can send crafted traffic that causes unpredictable or erroneous behavior and Denial of Service. The vulnerability is tracked under CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer).
Critical Impact
Remote unauthenticated attackers can disrupt Gateway availability and induce unstable behavior on NetScaler appliances exposed to the internet.
Affected Products
- Citrix NetScaler Application Delivery Controller (including FIPS and NDcPP variants)
- Citrix NetScaler Gateway
- NetScaler deployments configured as Gateway with PCoIP Profile bound
Discovery Timeline
- 2025-08-26 - CVE-2025-7776 published to NVD
- 2025-09-03 - Last updated in NVD database
Technical Details for CVE-2025-7776
Vulnerability Analysis
The vulnerability resides in the PCoIP (PC-over-IP) profile handling logic of NetScaler Gateway. PCoIP is a remote display protocol used to deliver virtual desktops and applications through the Gateway. When a NetScaler appliance is configured as a Gateway virtual server with a PCoIP Profile attached, the appliance processes PCoIP-related traffic on the data path. Improper restriction of operations within memory buffer bounds allows attacker-supplied input to overflow allocated memory regions. The result is unpredictable behavior, process instability, and a Denial of Service condition that disrupts remote access services. The exploitation path is network-reachable and does not require authentication or user interaction.
Root Cause
The root cause is improper memory boundary enforcement [CWE-119] within the PCoIP profile processing code. The affected component fails to validate the size or layout of incoming data structures before performing memory operations. This permits writes or reads beyond the intended buffer boundaries.
Attack Vector
Attackers reach the vulnerable code path remotely over the network by sending crafted protocol traffic to a NetScaler appliance configured as a Gateway with a PCoIP Profile binding. Configurations exposing VPN virtual servers, ICA Proxy, CVPN, or RDP Proxy with PCoIP enabled are reachable from untrusted networks in typical deployments. Successful exploitation degrades availability of the Gateway service and may corrupt in-process state. Citrix has not disclosed exploitation in the wild, and no public proof-of-concept is available at this time. See the Citrix Support Article CTX694938 for vendor technical details.
No verified exploit code is publicly available. Refer to the vendor advisory for protocol-level specifics.
Detection Methods for CVE-2025-7776
Indicators of Compromise
- Unexpected NetScaler nsppe or packet engine process crashes, restarts, or core dumps coinciding with inbound PCoIP traffic.
- Sudden loss of Gateway availability or session termination spikes on VPN virtual servers, ICA Proxy, CVPN, or RDP Proxy with PCoIP Profile bound.
- Anomalous inbound traffic patterns on PCoIP ports (TCP/UDP 4172) from untrusted source addresses.
Detection Strategies
- Audit NetScaler running configuration for bind vpn vserver entries that include a PCoIP Profile and inventory their internet exposure.
- Correlate NetScaler newnslog and syslog entries showing memory faults, segfaults, or watchdog restarts against Gateway access logs.
- Deploy network IDS signatures focused on malformed PCoIP session establishment toward NetScaler Gateway listeners.
Monitoring Recommendations
- Forward NetScaler appliance logs to a centralized SIEM or data lake and alert on packet engine restarts and abnormal connection resets.
- Continuously monitor Gateway virtual server health, CPU, and memory metrics for deviations from baseline.
- Track configuration drift to detect unauthorized binding or unbinding of PCoIP Profiles to Gateway virtual servers.
How to Mitigate CVE-2025-7776
Immediate Actions Required
- Apply the fixed NetScaler ADC and NetScaler Gateway firmware versions referenced in the Citrix Support Article CTX694938.
- Inventory all NetScaler appliances and identify those configured as Gateway with a PCoIP Profile bound.
- Restrict network exposure of NetScaler Gateway interfaces to required source ranges where feasible until patches are deployed.
Patch Information
Citrix has released firmware updates that remediate CVE-2025-7776 for supported NetScaler ADC and NetScaler Gateway branches, including FIPS and NDcPP builds. Customers running Citrix-managed NetScaler service do not need to take action. On-premises customers must upgrade to the fixed builds documented in the Citrix Support Article CTX694938. End-of-life versions do not receive fixes and must be migrated to supported releases.
Workarounds
- Unbind the PCoIP Profile from affected Gateway virtual servers if PCoIP is not required, which removes the vulnerable code path from the traffic flow.
- Disable or remove Gateway virtual servers that are not in active use to reduce the attack surface.
- Apply upstream access controls at firewalls or load balancers to restrict reachability of PCoIP listeners to trusted networks where business requirements permit.
# Identify Gateway virtual servers with a PCoIP Profile bound
show vpn vserver | grep -i pcoip
# Remove a PCoIP Profile binding if PCoIP is not required
unbind vpn vserver <vserver_name> -pcoipProfileName <profile_name>
# Verify the binding has been removed
show vpn vserver <vserver_name>
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
