CriticalCVE-2025-7775

    Memory overflow vulnerability leading to Remote Code Execution and/or Denial of Service (CVE-2025-7775)

    Published In CISA KEV since Sources: CVE.org, pwn.watch, CERT-EU, NCSC NZ

    What is affected, what to do

    A buffer overflow vulnerability in Citrix NetScaler ADC and NetScaler Gateway allows for remote code execution and/or denial of service. It affects specific configurations, including Gateway and AAA virtual servers, and versions 13.1, 14.1, 13.1-FIPS, and NDcPP. The vulnerability is actively exploited in the wild as of August 2025. Immediate patching to the latest version is critical to mitigate this risk.

    The vulnerability is being actively exploited; treat it as a priority. Update NetScaler ADC to version 47.48, NetScaler ADC to version 59.22, NetScaler ADC to version 37.241. Immediate actions, mitigation and detection rules are in the runbook below.

    Affected
    • NetScaler ADC lt 14.1..47.48
    • NetScaler ADC lt 13.1..59.22
    • NetScaler ADC lt 13.1 FIPS and NDcPP..37.241
    • NetScaler ADC lt 12.1 FIPS and NDcPP..55.330
    • NetScaler Gateway lt 14.1..47.48
    • NetScaler Gateway lt 13.1..59.22
    • NetScaler Gateway lt 13.1 FIPS and NDcPP..37.241
    • NetScaler Gateway lt 12.1 FIPS and NDcPP..55.330
    Fixed in
    • NetScaler ADC 47.48
    • NetScaler ADC 59.22
    • NetScaler ADC 37.241
    • NetScaler ADC 55.330
    • NetScaler Gateway 47.48
    • NetScaler Gateway 59.22
    • NetScaler Gateway 37.241
    • NetScaler Gateway 55.330

    Not sure whether and how you are affected? Ask a question about this vulnerability

    Metrics

    9.8

    Priority

    XIEM Effective CVSS: highest available CVSS rating from NVD and vendor data.

    Source: NVD, CVSS v3

    9.8

    CVSS v3

    Severity Critical on the scale from 0 to 10.

    Source: CVE.org, pwn.watch, CERT-EU, NCSC NZ

    20.3 %

    EPSS score

    Elevated — model estimates 10-50% exploitation likelihood.

    Source: FIRST EPSS, percentile 97.5

    Show all metrics
    Severity
    Critical
    Priority (0–325)

    The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first?

    Read in glossary
    235.66 Methodology
    Exploit maturity

    An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack.

    Read in glossary
    actively exploitedSource: VulnCheck KEV (opens in a new tab), ANSSI / CERT-FR How we classify
    XIEM Effective CVSS

    XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command.

    Read in glossary
    9.8 Methodology
    CVSS v3

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.8
    CVSS v4

    CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions.

    Read in glossary
    9.2
    EPSS score

    The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“.

    Read in glossary
    20.3 %
    Elevated — model estimates 10-50% exploitation likelihood.
    EPSS percentile

    The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking.

    Read in glossary
    97.5
    Critical — this CVE ranks in the top fifth of all CVEs scored today (rank ≥ 80%).
    KEV status

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    Actively exploited
    Published
    In CISA KEV since

    The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching.

    Read in glossary
    CWE

    CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect.

    Read in glossary
    CWE-119

    Response and mitigation

    Why act now?

    Prioritisation rationale

    This is unauthenticated, network-reachable code execution on a perimeter device that typically brokers identity and remote access, which makes it an ideal initial-access foothold. NetScaler gateways have repeatedly been mass-targeted for webshell persistence and onward lateral movement into corporate networks. Exploitation likelihood is very high, placing it among the CVEs most likely to be exploited. CISA does not flag known ransomware use, but treat any internet-facing appliance with Gateway, AAA, HDX or IPv6 LB configuration as critical: patch within 24 hours and run a mandatory compromise assessment. NIS2 entities should assess the 24-hour early-warning reporting obligation if compromise is confirmed.

    1. Runbook step 1

      Immediate response (0-24 h)

      • Establish exposure. Inventory every NetScaler ADC and NetScaler Gateway instance, including VPX/SDX/MPX and DR/test boxes, and run show ns version. Any build below 14.1-47.48, 13.1-59.22, 13.1-37.241 (FIPS/NDcPP) or 12.1-55.330 (FIPS/NDcPP) is vulnerable.
      • Patch now, starting with internet-facing Gateway and AAA appliances. Upgrade to 14.1-47.48, 13.1-59.22, 13.1-FIPS/NDcPP 13.1-37.241 or 12.1-FIPS/NDcPP 12.1-55.330 or later. Patch HA pairs completely: secondary first, then fail over, then patch the primary.
      • Confirm whether the vulnerable configuration is present so you can triage. Run shell grep -E "add (vpn|authentication|cr) vserver|add lb vserver" /nsconfig/ns.conf and look for:
        • VPN or AAA vservers
        • HDX CR vservers
        • HTTP/SSL/HTTP_QUIC LB vservers bound to IPv6 services or servicegroups, including DBS IPv6
      • Handle end-of-life releases. EOL builds, such as 12.1 and 13.0 non-FIPS, receive no fix. Pull them off the internet or migrate them to a supported branch.
      • Hunt for compromise before and after patching. The upgrade does not remove webshells or other persistence that is already in place. Take a forensic copy of /var/log, /var/core, /var/netscaler/logincustom, /netscaler/ns_gui and /var/vpn before upgrading.
      • Rotate secrets if any indicator fires. This includes:
        • LDAP/RADIUS bind accounts
        • nsroot and other local admin accounts
        • Certificate private keys stored on the appliance
        • Service credentials embedded in ns.conf

    2. Runbook step 2

      Mitigation layers

      • Network segmentation. Make management interfaces (NSIP, and any SNIP with management access) reachable only from a dedicated admin VLAN. Restrict appliance egress to what the service needs (DNS, NTP, auth back-ends, logging), then deny and log everything else.
      • Attack-surface reduction. Disable unused Gateway features (CVPN, RDP Proxy, ICA Proxy) and HDX CR vservers. Where operations allow, temporarily unbind IPv6 services from HTTP/SSL/HTTP_QUIC LB vservers or move them to IPv4 until the patch is applied.
      • Access restriction. Apply geo or IP allowlisting for Gateway vservers on the upstream firewall where feasible, for example limited to EU/DACH ranges and known partner networks. Enable vendor IPS signatures for CVE-2025-7775 on perimeter sensors and set them to block.
      • Availability protection. This flaw also causes DoS. Alert on packet-engine (nsppe) restarts and unplanned HA failovers, and treat them as possible exploitation attempts.
      • Integrity monitoring. Baseline hashes of /netscaler/ns_gui, /var/netscaler/logincustom and /var/vpn, for example with a cron job exporting to syslog. This lets you flag new PHP/XHTML/JS files automatically.

    3. Runbook step 3

      Detection rules

      • Webshell artefacts. On the appliance shell, run find /netscaler/ns_gui /var/netscaler/logincustom /var/vpn -type f \( -name "*.php" -o -name "*.xhtml" \) -mtime -30. Any new or modified file outside a firmware upgrade window is an indicator of compromise.
      • Crash indicators. Look for nsppe core dumps in /var/core/ and packet-engine restarts in /var/log/ns.log and /var/log/messages. SPL: index=netscaler ("nsppe" AND ("core" OR "restart" OR "crash")) | stats count by host.
      • Process ancestry. Alert on shells or tooling spawned by httpd, nsppe or nsaaad, such as sh, bash, python, perl, curl, wget, nc or base64. Sigma shape: ParentImage|endswith: ['/httpd','/nsppe'] AND Image|endswith: ['/sh','/bash','/curl','/nc']. Feed it from /var/log/bash.log or FreeBSD audit data.
      • Network telemetry (Zeek/Suricata). Alert on outbound sessions from NSIP/SNIP to uncatalogued external IPs, especially on odd ports or with long durations. KQL: CommonSecurityLog | where SourceIP in (netscaler_ips) and DestinationIP !in (allowlist) | summarize count() by DestinationIP, DestinationPort.
      • Access-log anomalies. Hunt for oversized or malformed HTTP and HTTP/3 (QUIC) requests to Gateway/AAA paths (/vpn/, /logon/, /cgi/, /oauth/) that are followed by 5xx responses or connection resets. Correlate their timestamps with crash events.

    Detection rules

    No NEOSEC detection rule is available for this vulnerability yet.

    Classification under NIS2 and CRA

    Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

    NIS2

    NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management.

    Read in glossary
    Actively exploited: treat the vulnerability as a priority in vulnerability handling under Art. 21(2)(e) NIS2. If it is exploited in your environment, check the reporting obligation under Art. 23 (early warning within 24 hours).
    CRA

    The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates.

    Read in glossary
    Since 11.09.2026, manufacturers of affected products with digital elements must report actively exploited vulnerabilities under Art. 14 CRA, with an early warning within 24 hours via ENISA's single reporting platform.
    ISO/IEC 27001

    ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security.

    Read in glossary
    Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

    Description

    Memory overflow vulnerability leading to Remote Code Execution and/or Denial of Service in NetScaler ADC and NetScaler Gateway when NetScaler is configured as Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server (OR) NetScaler ADC and NetScaler Gateway 13.1, 14.1, 13.1-FIPS and NDcPP: LB virtual servers of type (HTTP, SSL or HTTP_QUIC) bound with IPv6 services or servicegroups bound with IPv6 servers (OR) NetScaler ADC and NetScaler Gateway 13.1, 14.1, 13.1-FIPS and NDcPP: LB virtual servers of type (HTTP, SSL or HTTP_QUIC) bound with DBS IPv6 services or servicegroups bound with IPv6 DBS servers (OR) CR virtual server with type HDX

    Source: NVD (NIST), cvelistv5, CISA KEV Catalog, CVE.org (MITRE), pwn.watch, certeu_advisory, NCSC NZ (CC BY 4.0)

    Affected products

    The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

    Affected products
    Affected versionsFixed in
    NetScalerADC
    • 13.1 – < 59.22
    • 12.1 FIPS and NDcPP – < 55.330
    • 13.1 FIPS and NDcPP – < 37.241
    • 14.1 – < 47.48
    • 59.22
    • 55.330
    • 37.241
    • 47.48
    NetScalerGateway
    • 14.1 – < 47.48
    • 12.1 FIPS and NDcPP – < 55.330
    • 13.1 FIPS and NDcPP – < 37.241
    • 13.1 – < 59.22
    • 47.48
    • 55.330
    • 37.241
    • 59.22
    citrixnetscaler_application_delivery_controller
    • 12.1 – < 12.1-55.330
    • 13.1 – < 13.1-37.241
    • 13.1 – < 13.1-59.22
    • 14.1 – < 14.1-47.48
    • 12.1-55.330
    • 13.1-37.241
    • 13.1-59.22
    • 14.1-47.48
    citrixnetscaler_gateway
    • 13.1 – < 13.1-59.22
    • 14.1 – < 14.1-47.48
    • 13.1-59.22
    • 14.1-47.48

    Vendors and products

    Weakness classes (CWE)

    • CWE-119Improper Restriction of Operations within the Bounds of a Memory Buffer

      Class

      The product performs operations on a memory buffer, but it reads from or writes to a memory location outside the buffer's intended boundary. This may result in read or write operations on unexpected memory locations that could be linked to other variables, data structures, or internal program data.

      Entry at MITRE CWE-119

    Public exploit references

    Publicly reported proof-of-concepts, exploit modules and detection templates for this vulnerability. NEOSEC links to the original sources only and does not provide any exploit code.

    Public exploit references
    CISA KEV CatalogCISA Known Exploited Vulnerability (opens in a new tab)cisa.govactively exploited
    ANSSI / CERT-FRLicence Ouverte 2.0, as of CERTFR-2025-ALE-012 – Vulnérabilité dans Citrix NetScaler ADC et NetScaler Gateway (clôturée 2025-09-26) (opens in a new tab)cert.cyber.gouv.fractively exploited

    References & sources

    • support.citrix.comCitrix advisory: Citrix NetScalerVendor advisory, pwn-watch
    • cisa.govknown-exploited-vulnerabilities-catalog?field_cve=CVE-2025-7775government-resource, US government resource
    • cert.atCERT.at: Mehrere (teils kritische) Schwachstellen in NetScaler ADC and NetScaler Gatewaycert-at
    • cert.cyber.gouv.frANSSI / CERT-FR: CERTFR-2025-ALE-012 – Vulnérabilité dans Citrix NetScaler ADC et NetScaler Gateway (clôturée 2025-09-26)cert-fr
    • pwn.watchpwn.watch: Citrix NetScaler: NetScaler Memory Overflow Vulnerabilitypwn-watch
    • NVD (NIST)NVD: CVE-2025-7775pwn-watch
    • cisa.govCISA Known Exploited Vulnerabilities Catalogpwn-watch
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