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CVE-2026-88779 is a memory overflow vulnerability residing in the core architecture of Citrix NetScaler ADC and NetScaler Gateway appliances. The flaw specifically affects instances configured as SAML Service Provider (SP) or Identity Provider (IdP), where improper memory boundary validation during the processing of SAML authentication traffic allows an unauthenticated remote attacker to trigger memory out-of-bounds access (CWE-119). This leads to a memory overflow condition that can cause unpredictable behavior or a complete Denial of Service (DoS) on the affected appliance. The vulnerability spans multiple release branches, including ADC versions before 14.1-73.41, before 13.1-64.28, before 14.1-73.41 FIPS, and before 13.1-37.282, as well as Gateway versions before 14.1-73.41 and before 13.1-64.28. With a CVSS 4.0 base score of 8.7, the issue is rated HIGH severity due to its network-exploitable nature (AV:N), low attack complexity (AC:L), no required privileges (PR:N), and no user interaction (UI:N). The vector string `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N` confirms that the primary impact is on availability (VA:H), while confidentiality and integrity are unaffected. Successful exploitation can disrupt critical business applications, remote access services, and the entire backend infrastructure that relies on the NetScaler appliance as a perimeter defense. Organizations must treat this as an urgent perimeter security issue, as the appliance often serves as the primary entry point for remote users. Mitigation requires immediate patching to the specified fixed versions. In environments where immediate patching is not feasible, compensating controls such as restricting management interface access via strict IP whitelisting, network segmentation, and enhanced monitoring for anomalous SAML traffic patterns are strongly recommended. The vulnerability aligns with CWE-20 (Improper Input Validation) and maps to ATT&CK technique T1190 (Exploit Public-Facing Application) for initial access. As of publication, no public exploit or in-the-wild exploitation has been reported, but the severity and exposure of these appliances make proactive remediation imperative.
DailyCVE Form:
Platform: NetScaler ADC
Version: 14.1, 13.1
Vulnerability: Memory overflow
Severity: HIGH
date: 2026-10-04
Prediction: Patch available
What Undercode Say
Check current NetScaler ADC version via CLI ssh nsroot@<netscaler-ip> show ns version Check current NetScaler Gateway version via CLI show ns version Verify SAML configuration presence (SP/IdP) show samlAction show samlPolicy Check for vulnerable build strings show ns version | grep -E "14.1-73.[0-3][0-9]|13.1-64.[0-2][0-7]|13.1-37.[0-2][0-7]"
Python script to identify potentially vulnerable NetScaler versions
Educational use only - for inventory assessment
vulnerable_adc = [
"14.1-73.41", "13.1-64.28", "14.1-73.41 FIPS", "13.1-37.282"
]
vulnerable_gateway = [
"14.1-73.41", "13.1-64.28"
]
def check_version(product, current_version):
if product.lower() == "adc":
threshold = "14.1-73.41"
legacy = "13.1-64.28"
fips = "14.1-73.41 FIPS"
old_branch = "13.1-37.282"
if current_version in [threshold, legacy, fips, old_branch]:
return "VULNERABLE - immediate patching required"
elif product.lower() == "gateway":
threshold = "14.1-73.41"
legacy = "13.1-64.28"
if current_version in [threshold, legacy]:
return "VULNERABLE - immediate patching required"
return "Version not in known vulnerable set - verify manually"
Example usage
print(check_version("ADC", "14.1-73.40"))
print(check_version("Gateway", "13.1-64.27"))
Sample curl request to probe SAML endpoint (educational detection only) Do NOT run against systems you do not own or have permission to test curl -X POST https://<netscaler-ip>/saml/login \ -H "Content-Type: application/x-www-form-urlencoded" \ -d "SAMLRequest=<base64_encoded_payload>" \ --max-time 10 -v Monitor NetScaler logs for memory-related crashes tail -f /var/log/ns.log | grep -iE "memory|overflow|saml|crash|panic" Check system resource utilization during SAML traffic nscli -U :<nsroot-password> "stat system" | grep -i memory
Patch verification after upgrade show ns version show ns hardware show ns license Verify SAML functionality post-patch show samlAction show samlPolicy show samlStats
Exploit: (Educational Purposes!)
The exploit leverages the SAML authentication flow to trigger a memory overflow. An unauthenticated attacker sends a specially crafted SAML request to the NetScaler appliance. The appliance’s SAML handler fails to properly validate the memory boundary when processing the request, resulting in an out-of-bounds memory access. This can cause the appliance to crash, leading to a Denial of Service. In some scenarios, the memory corruption may be leveraged for further exploitation, though the primary confirmed impact is DoS. The attack requires the target to have SAML SP or IdP configuration enabled. The CVSS vector indicates no confidentiality or integrity impact, but high availability impact. Educational reproduction should only be performed in isolated lab environments with explicit authorization.
Protection: from this CVE
Upgrade NetScaler ADC to version 14.1-73.41 or later, or 13.1-64.28 or later. For FIPS deployments, upgrade to 14.1-73.41 FIPS or later. Upgrade NetScaler Gateway to 14.1-73.41 or later, or 13.1-64.28 or later. If immediate patching is not possible, restrict access to the management interface using strict IP whitelisting and network segmentation. Disable SAML SP/IdP functionality if not required. Enable advanced threat protection features and monitor for anomalous traffic patterns associated with exploitation attempts. Regularly review Citrix security advisories for updated guidance.
Impact
Successful exploitation results in a Denial of Service (DoS) condition on the NetScaler ADC or Gateway appliance. This disrupts critical business applications, remote access services, and backend infrastructure that rely on the appliance. Organizations may experience downtime, loss of productivity, and potential regulatory compliance violations due to service unavailability. The appliance often serves as the primary entry point for remote users, making its availability paramount for business continuity. While confidentiality and integrity are not directly impacted per the CVSS vector, the availability impact is rated HIGH (VA:H), indicating a significant disruption.
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Sources:
Reported By: www.cve.org
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