Our automated tracking framework flagged that CISA added CVE-2026-88771 (Citrix NetScaler) to the Known Exploited Vulnerabilities (KEV) catalog on September 28, 2026. A KEV listing is CISA’s official confirmation that the flaw is being exploited in the wild — U.S. federal agencies must patch it by a fixed deadline. Here is what our data shows.
What CISA Reported
CISA describes the flaw as follows: “Citrix NetScaler ADC and NetScaler Gateway contain an improper input validation vulnerability that could allow an unauthenticated attacker to execute arbitrary commands.”
Under Binding Operational Directive rules, U.S. federal agencies must remediate CVE-2026-88771 by September 30, 2026 — a 3-day window. Private organizations are not bound by the deadline, but CISA treats it as the benchmark for how urgently a confirmed-exploited flaw should be patched.
The Details
| CVE | CVE-2026-88771 |
| Vendor / product | Citrix NetScaler |
| Vulnerability | Citrix NetScaler Improper Input Validation Vulnerability |
| CVSS base score | 9.8 |
| Added to KEV | September 27, 2026 |
| Days public before listing (NVD → KEV lag) | 0 |
| Federal patch deadline | September 30, 2026 |
| Known ransomware use | No |
How This Compares to Citrix’s Track Record
This one was listed on or before its public disclosure (a lag of 0 days) — a zero-day exploited at or before the vulnerability was even published.
| Citrix in the CISA KEV catalog | Value |
|---|---|
| Tracked KEV entries | 26 |
| Median lag (public → KEV listing) | 47 days |
| 0-day rate (exploited at or before disclosure) | 27% |
| Entries tied to known ransomware campaigns | 7 |
For perspective, the median across all 1728 tracked KEV entries is 245 days — Citrix’s exploited vulnerabilities are flagged faster than the catalog average.
Other Recent Citrix KEV Additions
The most recent Citrix vulnerabilities CISA has confirmed as actively exploited, from our tracker:
| CVE | Product | Added to KEV | Lag (days) | Ransomware |
|---|---|---|---|---|
| CVE-2026-88772 | NetScaler | September 27, 2026 | 0 | No |
| CVE-2026-19490 | NetScaler | September 9, 2026 | 21 | No |
| CVE-2026-8452 | NetScaler ADC and NetScaler Gateway | August 26, 2026 | 57 | No |
| CVE-2026-3055 | NetScaler | March 30, 2026 | 7 | No |
| CVE-2025-7775 | NetScaler | August 26, 2025 | 0 | No |
Defense guide: How to Detect Zero-day Vulnerability: Attack Chain & Defense — detection signals, attack chain and response steps for this class of attack.
What This Means for Defenders
CISA has added CVE-2026-88771, an Improper Input Validation vulnerability in Citrix NetScaler, to its Known Exploited Vulnerabilities (KEV) catalog. With a CVSS base score of 9.8, it’s considered critical and demands immediate attention. Added to KEV on 2026-09-27 with a federal patch deadline of 2026-09-30, and a “days public before KEV listing” of 0, active exploitation was confirmed extremely rapidly. It indicates that attackers likely leveraged the vulnerability as a 0-day.
Organizations using Citrix NetScaler appliances must patch before the 2026-09-30 federal deadline. If you cannot apply the patch, restrict access to affected systems and enhance monitoring for unusual activity originating from or targeting NetScaler devices. Review access logs and network traffic for suspicious patterns to detect potential exploitation attempts. There isn’t any known ransomware use for this vulnerability.
Related Coverage
- Citrix’s CVE-2026-8452 Was Exploited in 57 Days — Faster Than Its 183-Day Median (August 2026)
- Citrix’s CVE-2026-19490 Was Exploited in 21 Days — Faster Than Its 120-Day Median (September 2026)
How We Track This
This report was generated from our CISA KEV Lag Tracker, which syncs the official CISA KEV catalog daily and records the date each CVE is added. For every entry we retrieve the original NVD publication date and compute the lag in calendar days. No dates or figures on this page are estimated or taken from third-party sources — they come directly from CISA and NVD records.
