Vulnerability report

Exploitation Attempts Observed Confirmed Confidence In CISA KEV

CVE-2026-88771

ADC Remote Code Execution

Citrix NetScaler / ADC · affected before 14.1-73.37

Watch CVE-2026-88771 Browse KEV feed
Severity
CVSS 9.5 · Critical
Confidence
Confirmed
Exploit status
Exploitation Attempts Observed in the Wild
EPSS
81.9%
First observed
29 Sep 2026
Last observed
14 Nov 2026

Decision summary

What security teams need to know first

Direct answers before the deeper technical record.

What it is

CVE-2026-88771 is an unauthenticated vulnerability affecting Citrix NetScaler ADC, Gateway. Improper input validation vulnerability in Citrix NetScaler ADC and Citrix NetScaler Gateway.

Have exploitation attempts been observed?

Yes. Previdian sensors have observed 557 exploitation attempts, 56 unique attacker IPs, and 18 countries targeting CVE-2026-88771. First observed Sep 29, 2026; last observed Nov 14, 2026. Listed in CISA KEV. Also reported by third-party sources. Confidence is confirmed.

Who is affected?

Citrix NetScaler / ADC and Gateway, including affected before 14.1-73.37, affected before 13.1-64.23, and affected before 14.1-73.37 FIPS.

What should we do?

Patch immediately, validate internet-facing exposure, and monitor for matching requests.

Overview

Improper input validation vulnerability in Citrix NetScaler ADC and Citrix NetScaler Gateway

Improper input validation vulnerability in Citrix NetScaler ADC and Citrix NetScaler Gateway.

This issue affects ADC: before 14.1-73.37, before 13.1-64.23, before 14.1-73.37 FIPS, and before 13.1.37.279 FIPS and NDcPP; Gateway: before 14.1-73.37 and before 13.1-64.23 leading to an unauthenticated attacker to execute arbitrary commands.

Citrix NetScaler Affected
ADC
Before 14.1-73.37 Before 13.1-64.23 Before 14.1-73.37 FIPS Before 13.1.37.279 FIPS and NDcPP
Citrix NetScaler Affected
Gateway
Before 14.1-73.37 Before 13.1-64.23
Published
27 Sep 2026
Exploitation Attempts Reported
27 Sep 2026
Attack vector
Remote
Complexity
Low
Privileges
None
User interaction
None

Tags

cisa metasploit_scanner

CVE References

Exploitation evidence

Evidence of exploitation attempts

Third-party attestation and first-party sensor observation are shown separately so teams can judge the evidence chain.

Exploitation Attempts Observed in the Wild

Citrix

Recorded 27 Sep 2026

A trusted third party reported exploitation attempts.

Exploitation Attempts Observed

Previdian sensor

First observed 29 Sep 2026

Previdian sensors observed exploitation attempts targeting this vulnerability.

Proof of concept available

GitHub

Recorded 27 Sep 2026

Public scanner or PoC coverage increases practical exploitability.

Known exploited vulnerability sources

Per-source evidence links for KEV attestations are available through the Previdian Pro API.

Learn about Pro API access
Source Added
Citrix First 2026-09-27 16:44 UTC
CVE 2026-09-27 20:40 UTC
Tenable Blog 2026-09-27 21:21 UTC
CISA 2026-09-27 21:50 UTC
The Hacker News 2026-09-28 07:30 UTC
SOCRadar 2026-09-28 08:20 UTC
CERT Polska 2026-09-28 08:21 UTC
Security Affairs 2026-09-28 10:21 UTC
Rapid7 2026-09-28 10:21 UTC
watchTowr 2026-09-28 11:20 UTC
NCSC Alerts and Advisories 2026-09-28 12:20 UTC
Palo Alto Unit42 2026-09-28 15:21 UTC
Qualys ThreatPROTECT 2026-09-28 16:20 UTC
GreyNoise 2026-09-28 17:21 UTC
The Shadowserver 2026-09-29 00:00 UTC
Google Threat Intelligence 2026-09-29 14:21 UTC
Arctic Wolf 2026-10-02 17:21 UTC
Previdian Sensors 2026-10-05 12:05 UTC

Operational indicators for this CVE are listed under Detection.

Sensor telemetry

Previdian Sensor Observations

Previdian sensor observations are exploitation attempts targeting this vulnerability. They do not show that the target was vulnerable or that the attempt succeeded. The cards and chart show volume, unique attackers, and daily activity.

557

Attempts observed

56

Unique attacker IPs

18

Attacker countries

BG · CN · CO · DE · HK · IN · JP · KR · LV · ML · NL · PA · RU · SC · SG · TW · UA · US

10

Sensors observed

CVE-2026-88771 exploitation attempts over the last 48 days

Daily events observed by Previdian sensors

Updated 14 Nov 2026

0
1
4
0
4
3
72
64
12
42
23
8
4
1
13
9
10
9
32
8
0
47
0
39
32
0
3
2
29
0
21
1
0
0
0
4
8
7
0
4
1
2
8
7
0
10
10
3
28 Sep 8 Oct 18 Oct 28 Oct 14 Nov

First observed 29 Sep 2026 · Last observed 14 Nov 2026

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Detection

Operational artifacts and observed signals

Make the evidence actionable in scanner, SOC, and edge-control workflows.

Observed signals

Request targets
User-Agents
Callback hosts
17
18
20

Request targets and User-Agents available in Pro. Callback host details available in Enterprise.

Virtual patch status

No Previdian virtual patch is currently available. Future rules ship for ModSecurity, Cloudflare, and AWS WAF.

Learn about virtual patches →

Attacker IP Indicators

Attacker IP indicators observed · available in Pro and Enterprise.

Sensor-derived attacker IP indicators are available to Pro and Enterprise accounts under Detection and through the Pro API.

Learn about Pro API access

Scanner Artifacts

Scanner and exploit-framework references linked to this CVE.

Scanner Reference Detected
Metasploit https://github.com/rapid7/metasploit-framework/blob/master/modules/exploits/freebsd/http/citrix_netscaler_cve_2026_88771.rb 27 Sep 2026

Risk and context

Severity, weaknesses, and research context

CVSS v4.0

9.5 Critical

Potential damage if exploited. Separate from whether attackers are using it.

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

EPSS

81.9%

Estimated chance of exploitation in the next 30 days. Previdian's warning comes from evidence, not this score.

Weaknesses

Improper Input Validation CWE-20

Recent mention · Rapid7

Metasploit Wrapup: Unauth RCE modules in Network Perimeter Devices and much more

Read full advisory

All CVSS Scores

CVSS v4.0 9.5 Critical

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

CVSS v3.1 9.8 Critical

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

All Mentions

Recent mention · The Hacker News

Critical FortiMail Zero-Day Flaw Exploited in Attacks Allows Unauthenticated Arbitrary File Writes

The Hacker News · 02 Oct 2026

Ravie LakshmananOct 02, 2026Vulnerability / Enterprise Security The U.S. Cybersecurity and Infrastructure Security Agency (CISA), on Thursday, added a critical security flaw impacting Fortinet FortiMail to its Known Exploited Vulnerabilities (KEV) catalog, following reports of active exploitation. The vulnerability, tracked as CVE-2026-104286 (CVSS score: 9.8), allows unauthenticated attackers to write arbitrary files on the underlying system. "An improper limitation of a pathname to a restricted directory ('path traversal') [CWE-22] and improper neutralization of NULL byte or NULL...

Recent mention · The Hacker News

Citrix NetScaler Post-Exploitation Payload Creates Superuser, Maps Web Shell to CSS-Like URLs

The Hacker News · 01 Oct 2026

Threat actors have been observed exploiting a critical pre-authentication command injection vulnerability in Citrix NetScaler ADC and NetScaler Gateway to drop web shells and attempt theft of configuration data. LevelBlue's Threat Hunt Operations & Research (THOR) team, which analyzed the exploitation activity across multiple customer environments, said it identified malicious NetScaler

Recent mention · The Hacker News

Attackers Exploit NetScaler Flaw for Root Access, Deploy WHIPSHOT and SLAPSHOT

The Hacker News · 30 Sep 2026

Ravie LakshmananSep 30, 2026Vulnerability / Web Security Unknown threat actors have been observed exploiting a newly patched security flaw in Citrix NetScaler ADC and NetScaler Gateway appliances to target organizations in North America and Europe. The activity, observed by Mandiant Consulting and Google Threat Intelligence Group (GTIG) in September 2026, has targeted government, financial services, technology, education, and legal and professional services sectors. "Exploitation of CVE-2026-88772 bypasses authentication and triggers an unhandled termination of the NetScaler Packet...

Recent mention · The Hacker News

Citrix NetScaler CVE-2026-88772 Exploit Details Show Pre-Auth Path to Shellcode Execution

The Hacker News · 30 Sep 2026

Ravie LakshmananSep 30, 2026Vulnerability / Network Security Cybersecurity researchers have disclosed technical details of a recently patched critical security flaw in Citrix NetScaler ADC and Gateway that has come under active exploitation in the wild. The vulnerability, tracked as CVE-2026-88772 (CVSS score: 9.5), has been described as a memory overflow bug in the Datagram Transport Layer Security (DTLS) protocol handling that's rooted in the NetScaler Packet Processing Engine (NSPPE). "Citrix NetScaler ADC and NetScaler Gateway contain an improper restriction of operations within the...

Recent mention · TheRegister

Custom malware used in Citrix 0-day attacks targeting govt, banks, professional services

TheRegister · 29 Sep 2026

Two questions remain: who is abusing the CVEs? And why did Citrix take so long to disclose?

Recent mention · Arctic Wolf

Critical Citrix NetScaler ADC and Citrix NetScaler Gateway Vulnerabilities

Arctic Wolf · 29 Sep 2026

Threat Summary On September 27th 2026, Citrix disclosed multiple vulnerabilities affecting NetScaler ADC and NetScaler Gateway. Arctic Wolf tracking indicates that CVE-2026-88771 and CVE-2026-88772 have been exploited in attacks against NetScaler devices as zero-days. Additional CVEs are also disclosed in the Citrix Security Bulletin. CVE-2026-88771 is an unauthenticated remote code execution vulnerability caused by improper ... Critical Citrix NetScaler ADC and Citrix NetScaler Gateway Vulnerabilities

Recent mention · Palo Alto Unit42

OperTraitors: How Kubernetes Operators Betray Your Security Posture

Palo Alto Unit42 · 29 Sep 2026

We introduce OperTraitor, a tool to audit privileges of Kubernetes operators, identify excessive RBAC risks, and secure non-human identities. The post OperTraitors: How Kubernetes Operators Betray Your Security Posture appeared first on Unit 42.

Recent mention · Google Threat Intelligence

Introduction In late September 2026, Mandiant Consulting and Google Threat Intelligence Group (GTIG) identified active, in-the-wild exploitation of...

Google Threat Intelligence · 29 Sep 2026

Introduction In late September 2026, Mandiant Consulting and Google Threat Intelligence Group (GTIG) identified active, in-the-wild exploitation of a zero-day vulnerability (CVE-2026-88772) affecting Citrix NetScaler ADC and NetScaler Gateway appliances. We have observed evidence that organizations in North America and Europe in the government, financial services, education, legal and professional services sectors were likely impacted by this exploitation campaign, which has been ongoing since at least early September. According to vendor disclosures, threat actors are also actively...

Recent mention · The Record

US, UK warn of exploited Citrix NetScaler zero-day bugs

The Record · 28 Sep 2026

Incident responders began warning of potential vulnerabilities in NetScaler Gateway products on Saturday before cybersecurity agencies in the Netherlands, U.S. and U.K. released advisories on Sunday confirming vulnerabilities. Citrix itself confirmed eight new vulnerabilities.

Recent mention · Qualys ThreatPROTECT

Citrix NetScaler ADC and Gateway Zero-day Vulnerabilities Exploited in Attacks (CVE-2026-88771 & CVE-2026-88772)

Qualys ThreatPROTECT · 28 Sep 2026

The Cybersecurity and Infrastructure Security Agency (CISA) has ordered agencies to secure their systems against two critical Citrix NetScaler vulnerabilities that have been exploited in attacks. CISA added CVE-2026-88771 and CVE-2026-88772 to its Known Exploited Vulnerabilities Catalog. CISA urged users to patch the vulnerabilities before September 30, 2026. CVE-2026-88771 This is an improper input validation … Continue reading "Citrix NetScaler ADC and Gateway Zero-day Vulnerabilities Exploited in Attacks (CVE-2026-88771 & CVE-2026-88772)"

Potential Proof of Concepts

These PoCs are unverified and could contain malware. Use at your own risk.

watchtowrlabs/watchTowr-vs-Citrix-Netscaler-CVE-2026-88771

github · Created 2026-09-27 18:15:38 UTC · 0 stars · AI assessment 85%

Timeline

From disclosure to observed exploitation attempts

  1. 17:21 UTC

    KEV confirmed by Arctic Wolf

    Exploitation attempts reported by an external source

  2. 14:21 UTC

    KEV confirmed by Google Threat Intelligence

    Exploitation attempts reported by an external source

  3. 01:02 UTC

    Indicators of compromise added (56)

    Indicators of compromise recorded

  4. 01:02 UTC

    Observed by Previdian sensors

    Previdian sensors observed exploitation attempts targeting this vulnerability.

  5. 00:00 UTC

    KEV confirmed by The Shadowserver

    Exploitation attempts reported by an external source

  6. 17:21 UTC

    KEV confirmed by GreyNoise

    Exploitation attempts reported by an external source

  7. 16:20 UTC

    KEV confirmed by Qualys ThreatPROTECT

    Exploitation attempts reported by an external source

  8. 15:21 UTC

    KEV confirmed by Palo Alto Unit42

    Exploitation attempts reported by an external source

  9. 12:20 UTC

    KEV confirmed by NCSC Alerts and Advisories

    Exploitation attempts reported by an external source

  10. 11:20 UTC

    KEV confirmed by watchTowr

    Exploitation attempts reported by an external source

  11. 10:21 UTC

    KEV confirmed by Rapid7

    Exploitation attempts reported by an external source

  12. 10:21 UTC

    KEV confirmed by Security Affairs

    Exploitation attempts reported by an external source

  13. 08:21 UTC

    KEV confirmed by CERT Polska

    Exploitation attempts reported by an external source

  14. 08:20 UTC

    KEV confirmed by SOCRadar

    Exploitation attempts reported by an external source

  15. 07:30 UTC

    KEV confirmed by The Hacker News

    Exploitation attempts reported by an external source

  16. 21:50 UTC

    Added to CISA KEV

    Listed in the CISA Known Exploited Vulnerabilities catalog

  17. 21:21 UTC

    KEV confirmed by Tenable Blog

    Exploitation attempts reported by an external source

  18. 20:40 UTC

    KEV confirmed by CVE

    Exploitation attempts reported by an external source

  19. 18:15 UTC

    Public PoC available

    Public proof-of-concept code published

  20. 16:44 UTC

    Added to Previdian KEV Feed

    High-confidence, third-party report of exploitation attempts

  21. 16:02 UTC

    CVE published

    Vulnerability disclosed publicly

  22. 00:00 UTC

    Metasploit module available

    Exploit module available

  23. 07:14 UTC

    CVE ID reserved

    Identifier reserved by the CNA

Pro API

Automate this intelligence

Confidence, exploit status, sensor telemetry, PoCs, scanner integrations, mentions, and tags are available programmatically for VM, SOC, and CTI workflows.

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  • Evidence confidence and provenance
  • First-party sensor telemetry
  • PoC and scanner references
  • Affected versions and enrichment
  • Automation-ready JSON delivery

GET /api/v2/pro/kevs/CVE-2026-88771

Sample API response 
{
  "cve_id": "CVE-2026-88771",
  "confidence": "Confirmed",
  "cvss_score": 9.5,
  "cvss_estimated": false,
  "epss_score": 0.81894,
  "exploit_status": {
    "exploited_in_the_wild": true,
    "active_exploitation_observed": true
  },
  "sensor_telemetry": { "attempts": 557, "sensors": 10 }
}