CVE-2026-88771: Citrix NetScaler

Should you act?

Exploited: patch now if you run it

CISA has confirmed exploitation in the wild. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

Yes, if you run Citrix NetScaler. CISA added this CVE to its Known Exploited Vulnerabilities catalog on 2026-09-27, which means there is reliable evidence of exploitation in the wild. US federal agencies must remediate by 2026-09-30; treat that as the outer limit, not the target.
EPSS 1.1%, percentile 65: FIRST’s model estimates a 1.1% chance of exploitation activity in the next 30 days, higher than 65% of all scored CVEs (moderate). EPSS is a probability, not a verdict.
Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
Editorial verdict: Act now. NetScaler CVE-2026-88771/88772: Exploited Pre-Auth RCE — Every customer-managed NetScaler ADC or Gateway needs the latest build today, and any appliance that was unpatched in September should be investigated as compromised, because patching does not evict attackers.

What it is

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.

CISA’s summary

Citrix NetScaler ADC and NetScaler Gateway contain an improper input validation vulnerability that could allow an unauthenticated attacker to execute arbitrary commands.

Weakness type: CWE-20, CWE-119.

Product: Citrix NetScaler · Assigned by: NetScaler · Published: 2026-09-27

Affected and fixed versions

Vendor	Product	Affected versions (per CVE record)
Citrix NetScaler	ADC	< 14.1-73.37, < 13.1-64.23, < 14.1-73.37 FIPS, < 13.1.37.279 FIPS and NDcPP
Citrix NetScaler	Gateway	< 14.1-73.37, < 13.1-64.23

Severity scores

Scored by	CVSS	Score	Vector
NetScaler	4.0	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`

Attack vector: network (remotely reachable)
Attack complexity: low
Attack requirements: present (depends on deployment conditions)
Privileges required: none (no login)
User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

CISA KEV: added 2026-09-27; federal due date 2026-09-30. Known ransomware use: Unknown.
CISA required action: Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.
CISA SSVC assessment: exploitation active, automatable yes, technical impact total.
FIRST EPSS (model of 2026-10-21): 1.08% probability of exploitation activity in the next 30 days; percentile 65.

Timeline

2026-09-27 — Added to CISA’s Known Exploited Vulnerabilities catalog
2026-09-27 — CVE record published by NetScaler
2026-09-27 — erroneo.us brief: NetScaler CVE-2026-88771/88772: Exploited Pre-Auth RCE
2026-09-29 — CVE record last updated
2026-09-30 — CISA remediation deadline for US federal agencies

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.