NCSC-2026-0394
Vulnerability from csaf_ncscnl - Published: 2026-09-27 16:55 - Updated: 2026-09-30 08:38An input validation vulnerability in Citrix NetScaler ADC and Gateway allows unauthenticated attackers to execute arbitrary commands remotely.
| Product | Identifier | Version | Remediation |
|---|---|---|---|
|
vers:unknown/*
Citrix / NetScaler ADC
|
vers:unknown/* | ||
|
vers:unknown/*
Citrix / NetScaler Gateway
|
vers:unknown/* |
A memory overflow vulnerability in Citrix NetScaler ADC and Gateway prior to specified updates can lead to remote code execution or denial of service.
A vulnerability known as HTTP Request/Response Smuggling, caused by inconsistent HTTP request interpretation, affects multiple versions of Citrix NetScaler ADC and Gateway prior to specified updates.
A vulnerability in Citrix NetScaler ADC and Gateway prior to specified updates allows feature policy bypass due to improper use of HTTP URL based expressions.
A memory overflow vulnerability in Citrix NetScaler ADC and Gateway versions prior to specified updates can cause unpredictable behavior or Denial of Service, impacting system stability and availability.
A memory overflow vulnerability in Citrix NetScaler ADC and Gateway versions prior to specified updates can cause unpredictable behavior or Denial of Service conditions.
A memory overflow vulnerability in Citrix NetScaler ADC and Gateway versions prior to specified updates can cause unpredictable behavior or Denial of Service conditions.
A TCP Initial Sequence Number (ISN) prediction vulnerability affects Citrix NetScaler ADC and Gateway versions prior to 14.1-73.37 and 13.1-64.23, allowing predictable exact values from previous values.
{
"document": {
"category": "csaf_security_advisory",
"csaf_version": "2.0",
"distribution": {
"tlp": {
"label": "WHITE"
}
},
"lang": "nl",
"notes": [
{
"category": "legal_disclaimer",
"text": "The Netherlands Cyber Security Center (henceforth: NCSC-NL) maintains this page to enhance access to its information and security advisories. The use of this security advisory is subject to the following terms and conditions:\n\n NCSC-NL makes every reasonable effort to ensure that the content of this page is kept up to date, and that it is accurate and complete. Nevertheless, NCSC-NL cannot entirely rule out the possibility of errors, and therefore cannot give any warranty in respect of its completeness, accuracy or continuous keeping up-to-date. The information contained in this security advisory is intended solely for the purpose of providing general information to professional users. No rights can be derived from the information provided therein.\n\n NCSC-NL and the Kingdom of the Netherlands assume no legal liability or responsibility for any damage resulting from either the use or inability of use of this security advisory. This includes damage resulting from the inaccuracy of incompleteness of the information contained in the advisory.\n This security advisory is subject to Dutch law. All disputes related to or arising from the use of this advisory will be submitted to the competent court in The Hague. This choice of means also applies to the court in summary proceedings."
},
{
"category": "description",
"text": "Citrix heeft 8 kwetsbaarheden verholpen in NetScaler ADC en NetScaler Gateway. De volgende ondersteunde versies van Citrix NetScaler ADC en Citrix NetScaler Gateway zijn kwetsbaar:\n\n- Citrix NetScaler ADC en Citrix NetScaler Gateway 14.1 v\u00f3\u00f3r versie 14.1-73.37\n- Citrix NetScaler ADC en Citrix NetScaler Gateway 13.1 v\u00f3\u00f3r versie 13.1-64.23\n- Citrix NetScaler ADC FIPS v\u00f3\u00f3r versie 14.1-73.37 FIPS\n- Citrix NetScaler ADC FIPS en NDcPP v\u00f3\u00f3r versie 13.1-37.279\n\nSecure Private Access Hybrid-implementaties die gebruikmaken van NetScaler-instances zijn ook kwetsbaar voor deze kwetsbaarheden.\n\nDeze advisory is uitsluitend van toepassing op door klanten beheerde Citrix NetScaler ADC-systemen (\u201cNetScaler ADC\u201d) en Citrix NetScaler Gateway-systemen (\u201cNetScaler Gateway\u201d). Cloud Software Group voorziet de door Citrix beheerde clouddiensten en Citrix Managed Adaptive Authentication van de benodigde software-updates. ",
"title": "Feiten"
},
{
"category": "description",
"text": "De kwetsbaarheden betreffen verschillende beveiligingsproblemen die onder meer kunnen leiden tot Remote Code Execution (RCE), HTTP Request Smuggling, het omzeilen van beleidsregels en Denial-of-Service. Drie kwetsbaarheden met kenmerk CVE-2026-88771, CVE-2026-88772 en CVE-2026-88773 zijn als kritiek aangemerkt.\n\nDe kwetsbaarheid met kenmerk CVE-2026-88771 heeft een CVSS-score van 9,5 en betreft onvoldoende invoervalidatie. Een niet-geauthenticeerde kwaadwillende kan op afstand willekeurige commando\u0027s uitvoeren. Volgens Citrix zijn alle NetScaler ADC- en NetScaler Gateway-deployments getroffen en is geen aanvullende functionaliteit of specifieke configuratie voor misbruik vereist.\n\nDe kwetsbaarheid met kenmerk CVE-2026-88772 heeft een CVSS-score van 9,5 en betreft een memory overflow die kan leiden tot RCE of Denial-of-Service. Misbruik is mogelijk wanneer DTLS is ingeschakeld. Citrix geeft aan dat DTLS standaard is ingeschakeld op een VPN virtual server.\n\nDe kwetsbaarheid met kenmerk CVE-2026-88773 heeft een CVSS-score van 9,3 en betreft HTTP Request Smuggling. Voor misbruik moet HTTP-functionaliteit zijn ingeschakeld op NetScaler ADC of NetScaler Gateway. Authenticatie en gebruikersinteractie zijn niet vereist.\n\nDe kwetsbaarheid met kenmerk CVE-2026-88774 heeft een CVSS-score van 7,0 en kan leiden tot het omzeilen van een feature policy door onjuist gebruik van HTTP URL-gebaseerde policy expressions. De kwetsbaarheid is alleen van toepassing wanneer dergelijke expressions zijn geconfigureerd.\n\nDe kwetsbaarheid met kenmerk CVE-2026-88775 heeft een CVSS-score van 8,8 en betreft een memory overflow die kan leiden tot onvoorspelbaar gedrag of Denial-of-Service. De kwetsbaarheid is van toepassing op systemen die zijn geconfigureerd als Gateway, waaronder SSL VPN, ICA Proxy, CVPN en RDP Proxy, of als AAA virtual server.\n\nDe kwetsbaarheid met kenmerk CVE-2026-88776 heeft een CVSS-score van 8,8 en betreft eveneens een memory overflow die kan leiden tot onvoorspelbaar gedrag of Denial-of-Service. Voor misbruik moet een load-balancing virtual server van het type Oracle zijn geconfigureerd.\n\nDe kwetsbaarheid met kenmerk CVE-2026-88777 heeft een CVSS-score van 8,8 en betreft een memory overflow die kan leiden tot onvoorspelbaar gedrag of Denial-of-Service. De kwetsbaarheid vereist een LB-, CS- of CGNAT-LSN/NAT64-configuratie waarbij een non-HTTP Layer 7-protocol is ingeschakeld.\n\nDe kwetsbaarheid met kenmerk CVE-2026-88778 heeft een CVSS-score van 8,8 en betreft voorspelbaarheid van TCP Initial Sequence Numbers (ISN). Voor misbruik moet TCP-functionaliteit zijn ingeschakeld op NetScaler ADC of NetScaler Gateway.\n\nCitrix meldt dat misbruik van de kwetsbaarheden met kenmerk CVE-2026-88771 en CVE-2026-88772 zijn waargenomen op NetScaler-systemen.\n\n",
"title": "Interpretaties"
},
{
"category": "description",
"text": "Citrix heeft beveiligingsupdates uitgebracht om de kwetsbaarheden te verhelpen. Het NCSC adviseert om de beveiligingsupdates met spoed toe te passen. Het installeren van de update voorkomt nieuw misbruik, maar sluit niet uit dat eerder al misbruik heeft plaatsgevonden. Voordat de update wordt doorgevoerd, wordt geadviseerd relevante logging en een memory dump veilig te stellen. Hierdoor blijft mogelijk forensisch bewijsmateriaal beschikbaar voor onderzoek naar eerder misbruik. \n\nVanwege het bevestigde misbruik van de kwetsbaarheden met kenmerk CVE-2026-88771 en CVE-2026-88772 wordt geadviseerd om bij systemen die v\u00f3\u00f3r het installeren van de update vanaf het internet toegankelijk waren, rekening te houden met mogelijke eerdere compromittatie.\n\nCitrix heeft via NetScaler Console een scanscript en indicators-of-compromised (IoC\u0027s) beschikbaar gesteld. Klanten kunnen met dit script controleren of hun NetScaler-omgeving mogelijk is getroffen. Klanten die geen gebruikmaken van NetScaler Console, dienen contact op te nemen met Citrix Support om toegang aan te vragen tot de relevante generieke IoC\u0027s.\n\nZie bijgevoegde referenties voor meer informatie.",
"title": "Oplossingen"
},
{
"category": "general",
"text": "high",
"title": "Kans"
},
{
"category": "general",
"text": "high",
"title": "Schade"
},
{
"category": "general",
"text": "Predictable Exact Value from Previous Values",
"title": "CWE-342"
},
{
"category": "general",
"text": "Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)",
"title": "CWE-444"
}
],
"publisher": {
"category": "coordinator",
"contact_details": "cert@ncsc.nl",
"name": "Nationaal Cyber Security Centrum",
"namespace": "https://www.ncsc.nl/"
},
"references": [
{
"category": "external",
"summary": "Reference",
"url": "https://community.citrix.com/techzone-blogs/110_security-updates/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve-2026-88771-through-cve-2026-88778/#Indicators_of_Compromise__cabcb4"
},
{
"category": "external",
"summary": "Reference",
"url": "https://support.citrix.com/support-home/kbsearch/article?articleNumber=CTX697096\u0026articleTitle=Citrix_NetScaler_ADC_and_Citrix_NetScaler_Gateway_Security_Bulletin_for_CVE_2026_88771_CVE_2026_88772_CVE_2026_88773_CVE_2026_88774_CVE_2026_88775_CVE_2026_88776_CVE_2026_88777_and_CVE_2026_88778"
}
],
"title": "Kwetsbaarheden verholpen in NetScaler ADC en NetScaler Gateway",
"tracking": {
"current_release_date": "2026-09-30T08:38:43.031636Z",
"generator": {
"date": "2025-08-04T16:30:00Z",
"engine": {
"name": "V.A.",
"version": "1.3"
}
},
"id": "NCSC-2026-0394",
"initial_release_date": "2026-09-27T16:55:29.765476Z",
"revision_history": [
{
"date": "2026-09-27T16:55:29.765476Z",
"number": "1.0.0",
"summary": "Initiele versie"
},
{
"date": "2026-09-30T08:38:43.031636Z",
"number": "1.0.1",
"summary": "Handelingsperspectief uitgebreid met informatie over het scanscript en IoC\u0027s."
}
],
"status": "final",
"version": "1.0.1"
}
},
"product_tree": {
"branches": [
{
"branches": [
{
"branches": [
{
"category": "product_version_range",
"name": "vers:unknown/*",
"product": {
"name": "vers:unknown/*",
"product_id": "CSAFPID-1"
}
}
],
"category": "product_name",
"name": "NetScaler ADC"
},
{
"branches": [
{
"category": "product_version_range",
"name": "vers:unknown/*",
"product": {
"name": "vers:unknown/*",
"product_id": "CSAFPID-2"
}
}
],
"category": "product_name",
"name": "NetScaler Gateway"
}
],
"category": "vendor",
"name": "Citrix"
}
]
},
"vulnerabilities": [
{
"cve": "CVE-2026-88771",
"notes": [
{
"category": "description",
"text": "An input validation vulnerability in Citrix NetScaler ADC and Gateway allows unauthenticated attackers to execute arbitrary commands remotely.",
"title": "Summary"
},
{
"category": "general",
"text": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H",
"title": "CVSSV4"
}
],
"product_status": {
"known_affected": [
"CSAFPID-1",
"CSAFPID-2"
]
},
"references": [
{
"category": "self",
"summary": "CVE-2026-88771 | NCSC-NL Website",
"url": "https://vulnerabilities.ncsc.nl/csaf/v2/2026/cve-2026-88771.json"
}
],
"scores": [
{
"cvss_v3": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"products": [
"CSAFPID-1",
"CSAFPID-2"
]
}
],
"title": "CVE-2026-88771"
},
{
"cve": "CVE-2026-88772",
"notes": [
{
"category": "description",
"text": "A memory overflow vulnerability in Citrix NetScaler ADC and Gateway prior to specified updates can lead to remote code execution or denial of service.",
"title": "Summary"
},
{
"category": "general",
"text": "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",
"title": "CVSSV4"
}
],
"product_status": {
"known_affected": [
"CSAFPID-1",
"CSAFPID-2"
]
},
"references": [
{
"category": "self",
"summary": "CVE-2026-88772 | NCSC-NL Website",
"url": "https://vulnerabilities.ncsc.nl/csaf/v2/2026/cve-2026-88772.json"
}
],
"scores": [
{
"cvss_v3": {
"baseScore": 8.1,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"products": [
"CSAFPID-1",
"CSAFPID-2"
]
}
],
"title": "CVE-2026-88772"
},
{
"cve": "CVE-2026-88773",
"cwe": {
"id": "CWE-444",
"name": "Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)"
},
"notes": [
{
"category": "other",
"text": "Inconsistent Interpretation of HTTP Requests (\u0027HTTP Request/Response Smuggling\u0027)",
"title": "CWE-444"
},
{
"category": "description",
"text": "A vulnerability known as HTTP Request/Response Smuggling, caused by inconsistent HTTP request interpretation, affects multiple versions of Citrix NetScaler ADC and Gateway prior to specified updates.",
"title": "Summary"
},
{
"category": "general",
"text": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:H/SI:H/SA:N",
"title": "CVSSV4"
}
],
"product_status": {
"known_affected": [
"CSAFPID-1",
"CSAFPID-2"
]
},
"references": [
{
"category": "self",
"summary": "CVE-2026-88773 | NCSC-NL Website",
"url": "https://vulnerabilities.ncsc.nl/csaf/v2/2026/cve-2026-88773.json"
}
],
"scores": [
{
"cvss_v3": {
"baseScore": 10.0,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:N",
"version": "3.1"
},
"products": [
"CSAFPID-1",
"CSAFPID-2"
]
}
],
"title": "CVE-2026-88773"
},
{
"cve": "CVE-2026-88774",
"notes": [
{
"category": "description",
"text": "A vulnerability in Citrix NetScaler ADC and Gateway prior to specified updates allows feature policy bypass due to improper use of HTTP URL based expressions.",
"title": "Summary"
},
{
"category": "general",
"text": "CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:L/VI:L/VA:N/SC:H/SI:H/SA:N",
"title": "CVSSV4"
}
],
"product_status": {
"known_affected": [
"CSAFPID-1",
"CSAFPID-2"
]
},
"references": [
{
"category": "self",
"summary": "CVE-2026-88774 | NCSC-NL Website",
"url": "https://vulnerabilities.ncsc.nl/csaf/v2/2026/cve-2026-88774.json"
}
],
"scores": [
{
"cvss_v3": {
"baseScore": 7.2,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N",
"version": "3.1"
},
"products": [
"CSAFPID-1",
"CSAFPID-2"
]
}
],
"title": "CVE-2026-88774"
},
{
"cve": "CVE-2026-88775",
"cwe": {
"id": "CWE-120",
"name": "Buffer Copy without Checking Size of Input (\u0027Classic Buffer Overflow\u0027)"
},
"notes": [
{
"category": "other",
"text": "Buffer Copy without Checking Size of Input (\u0027Classic Buffer Overflow\u0027)",
"title": "CWE-120"
},
{
"category": "description",
"text": "A memory overflow vulnerability in Citrix NetScaler ADC and Gateway versions prior to specified updates can cause unpredictable behavior or Denial of Service, impacting system stability and availability.",
"title": "Summary"
},
{
"category": "general",
"text": "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",
"title": "CVSSV4"
}
],
"product_status": {
"known_affected": [
"CSAFPID-1",
"CSAFPID-2"
]
},
"references": [
{
"category": "self",
"summary": "CVE-2026-88775 | NCSC-NL Website",
"url": "https://vulnerabilities.ncsc.nl/csaf/v2/2026/cve-2026-88775.json"
}
],
"scores": [
{
"cvss_v3": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"products": [
"CSAFPID-1",
"CSAFPID-2"
]
}
],
"title": "CVE-2026-88775"
},
{
"cve": "CVE-2026-88776",
"notes": [
{
"category": "description",
"text": "A memory overflow vulnerability in Citrix NetScaler ADC and Gateway versions prior to specified updates can cause unpredictable behavior or Denial of Service conditions.",
"title": "Summary"
},
{
"category": "general",
"text": "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",
"title": "CVSSV4"
}
],
"product_status": {
"known_affected": [
"CSAFPID-1",
"CSAFPID-2"
]
},
"references": [
{
"category": "self",
"summary": "CVE-2026-88776 | NCSC-NL Website",
"url": "https://vulnerabilities.ncsc.nl/csaf/v2/2026/cve-2026-88776.json"
}
],
"scores": [
{
"cvss_v3": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"products": [
"CSAFPID-1",
"CSAFPID-2"
]
}
],
"title": "CVE-2026-88776"
},
{
"cve": "CVE-2026-88777",
"notes": [
{
"category": "description",
"text": "A memory overflow vulnerability in Citrix NetScaler ADC and Gateway versions prior to specified updates can cause unpredictable behavior or Denial of Service conditions.",
"title": "Summary"
},
{
"category": "general",
"text": "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",
"title": "CVSSV4"
}
],
"product_status": {
"known_affected": [
"CSAFPID-1",
"CSAFPID-2"
]
},
"references": [
{
"category": "self",
"summary": "CVE-2026-88777 | NCSC-NL Website",
"url": "https://vulnerabilities.ncsc.nl/csaf/v2/2026/cve-2026-88777.json"
}
],
"scores": [
{
"cvss_v3": {
"baseScore": 9.8,
"baseSeverity": "CRITICAL",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H",
"version": "3.1"
},
"products": [
"CSAFPID-1",
"CSAFPID-2"
]
}
],
"title": "CVE-2026-88777"
},
{
"cve": "CVE-2026-88778",
"cwe": {
"id": "CWE-342",
"name": "Predictable Exact Value from Previous Values"
},
"notes": [
{
"category": "other",
"text": "Predictable Exact Value from Previous Values",
"title": "CWE-342"
},
{
"category": "description",
"text": "A TCP Initial Sequence Number (ISN) prediction vulnerability affects Citrix NetScaler ADC and Gateway versions prior to 14.1-73.37 and 13.1-64.23, allowing predictable exact values from previous values.",
"title": "Summary"
},
{
"category": "general",
"text": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:H/VA:H/SC:L/SI:L/SA:L",
"title": "CVSSV4"
}
],
"product_status": {
"known_affected": [
"CSAFPID-1",
"CSAFPID-2"
]
},
"references": [
{
"category": "self",
"summary": "CVE-2026-88778 | NCSC-NL Website",
"url": "https://vulnerabilities.ncsc.nl/csaf/v2/2026/cve-2026-88778.json"
}
],
"scores": [
{
"cvss_v3": {
"baseScore": 7.5,
"baseSeverity": "HIGH",
"vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N",
"version": "3.1"
},
"products": [
"CSAFPID-1",
"CSAFPID-2"
]
}
],
"title": "CVE-2026-88778"
}
]
}
Sightings
| Author | Source | Type | Date | Other |
|---|
Nomenclature
- Seen: The vulnerability was mentioned, discussed, or observed by the user.
- Confirmed: The vulnerability has been validated from an analyst's perspective.
- Published Proof of Concept: A public proof of concept is available for this vulnerability.
- Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
- Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
- Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
- Not confirmed: The user expressed doubt about the validity of the vulnerability.
- Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
Browse all ATT&CK techniques and the vulnerabilities related to each.
Related by attack behaviour
Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.