Citrix · NetScaler ADC and NetScaler Gateway
CVE-2023-6549
Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability
What it is
Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway allows Unauthenticated Denial of Service and Out-Of-Bounds Memory Read
CISA: Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow vulnerability that allows for a denial-of-service when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.
What to do
Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.
Deadline for US federal agencies: February 7, 2024
More exploited flaws from Citrix
| Added | Vulnerability | Product | Severity | Attack chance |
|---|---|---|---|---|
| Aug 26, 2026 | Improper Restriction of Operations within the Bounds of a Memory Buffer | NetScaler ADC and NetScaler Gateway | High 8.8 | 1.0% |
| Jan 17, 2024 | Code Injection | NetScaler ADC and NetScaler Gateway | Medium 5.5 | 3.2% |
| Oct 18, 2023 | Buffer Overflow | NetScaler ADC and NetScaler Gateway | Critical 9.4 | >99.9% |
| Jul 19, 2023 | Code Injection | NetScaler ADC and NetScaler Gateway | Critical 9.8 | 99.7% |
| Oct 4, 2026 | Improper Restriction of Operations within the Bounds of a Memory Buffer | NetScaler | High 8.7 | 11% |
| Sep 27, 2026 | Improper Input Validation | NetScaler | Critical 9.5 | 82% |
| Sep 27, 2026 | Improper Restriction of Operations within the Bounds of a Memory Buffer | NetScaler | Critical 9.5 | 78% |
| Sep 9, 2026 | Authentication Bypass Using an Alternate Path or Channel | NetScaler | Critical 9.3 | 33% |
Sources: Known Exploited Vulnerabilities (CISA, public domain), CVE records (cve.org) and EPSS (FIRST). The chance of attacks is the EPSS estimate that someone will try to exploit the flaw in the next 30 days.