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Citrix NetScaler Improper Input Validation Vulnerability

Exploited · KEV 2026-09-27Metasploit moduleCVE-2026-88771CWE-20

Exploited since 2026-09-27. 2 of 8 rule sources name it; Cloudflare blocks by default.

Edge rules
2/8
Our test
No exploit yet
CVSS
9.5
EPSS
82.2% Top 0.3%
Posts, 14d
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Published
2026-09-27
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… More

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.

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Ask about CVE-2026-88771: who's covered, what to patch first, how vendors compare. I cite sources and won't help with attacks.

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Severity, decoded

CVSS 4.0
Critical · 9.5 / 10

Exploitable over the network under specific conditions, with no privileges and no user interaction, leading to full loss of confidentiality, integrity and availability; other systems can also be hit (full loss of confidentiality, integrity and availability).

Over the internetNo login neededNo user actionWorks reliablySpreads beyond the appFull compromise
How the score is built11 metrics
  • Attack vectorAn attacker can reach it over the internet; no access to your network needed.
    Network
  • Attack complexityNo built-in defences have to be bypassed; the attack works reliably.
    Low
  • Attack requirementsThe attack only works under specific conditions, such as a race or a particular setup.
    Present
  • Privileges requiredNo account or login is needed.
    None
  • User interactionNo one has to click or open anything; the attack works on its own.
    None
  • Confidentiality impact (vulnerable system)An attacker can read all data the affected component holds, or the most sensitive parts of it.
    High
  • Integrity impact (vulnerable system)An attacker can change any data or files the affected component protects.
    High
  • Availability impact (vulnerable system)An attacker can take the component down completely or keep it from serving anyone.
    High
  • Confidentiality impact (other systems)Other systems that rely on it can have all their data read.
    High
  • Integrity impact (other systems)Other systems that rely on it can have any data changed.
    High
  • Availability impact (other systems)Other systems that rely on it can be taken down.
    High
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
CISA's assessmentSSVC, from the CVE record
ExploitationActive

Attackers are exploiting this in the wild.

AutomatableYes

Attackers can script the attack end to end and hit many targets at once.

Technical impactTotal

A successful attack gives full control over the affected software or all of its data.

Public exploits

1 found
1 Metasploit0 Exploit-DB0 Scanner template0 GitHub PoCs

Links are to third-party code: never run it outside an isolated lab.

Timeline

  1. 2026-09-27
    CVE published
    CVE List
  2. 2026-09-27
    Added to CISA KEV
    Confirmed exploitation in the wild
  3. 2026-09-27
    Metasploit module published
    Citrix NetScaler Unauthenticated Login Log Command Injection (CVE-2026-88771)
  4. 2026-10-01
    Cloudflare ships a rule
    Citrix Netscaler ADC and Gateway - Improper input validation - CVE:CVE-2026-88771
  5. 2026-10-21
    F5 ships a rule
    Citrix Netscaler Remote Code Execution (2)

Social

2026-10-20: 0 posts2026-10-21: 0 posts2026-10-22: 0 posts2026-10-23: 0 posts2026-10-24: 0 posts2026-10-25: 0 posts2026-10-26: 0 posts2026-10-27: 0 posts2026-10-28: 0 posts2026-10-29: 0 posts2026-10-30: 0 posts2026-10-31: 0 posts2026-11-01: 0 posts2026-11-02: 0 posts

No posts seen yet on X, Bluesky, Mastodon, Hacker News or GitHub.

Vendor statements

Quoted
CloudflareWAF Managed Rules1 quoteBlocks by default

First rule 2026-10-01, 4 days after the CVE was published.

2026-10-01New rule…827ab216Default: BlockSource
Citrix Netscaler ADC and Gateway - Improper input validation - CVE:CVE-2026-88771. Previous action: N/A. New action: Block. This is a new detection.
AWSAWS WAF Managed RulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. AWS often describes a vulnerability without naming its CVE (for example "Log4j"). We count only entries that name the CVE, so AWS coverage is understated.

Microsoft AzureFront Door and Application Gateway WAF (DRS)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. The rule tables name CVEs but carry no dates, so Azure is left out of every time-to-rule figure.

Google CloudCloud Armor preconfigured WAF rulesNo public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. Google names few CVEs: the release notes start in May 2024 and the rules reference lists CVEs without dates. Its cve-canary rules are opt-in.

FastlyNext-Gen WAF virtual patchesBefore feed history

The CVE predates the oldest entry in this vendor's public feed, so a rule may exist that we cannot see.

F5Attack signatures (Distributed Cloud WAF)1 quoteRule published

First rule 2026-10-21, 24 days after the CVE was published.

2026-10-21New rule200103695Source
Added: signature 200103695 "Citrix Netscaler Remote Code Execution (2)" (Command Execution, risk High), systems: Citrix. References: CVE-2026-88771.
AkamaiApp & API Protector (Adaptive Security Engine)No public source

This vendor publishes no machine-readable rule changelog we can check.

OWASP CRSCore Rule Set (open source, used inside many WAFs)No public claim

We found no public statement from this vendor naming this CVE. That is not proof of no protection: generic rules may still catch it. CRS rarely names CVEs: it relies on generic detections. Our own lab measures what it actually blocks.