CVE-2023-4966
HighExploitedPublic exploitSensitive information disclosure in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.
Published Oct 11, 2023 · Updated Jul 31, 2026 · Also known as Citrix Bleed, CitrixBleed, TR-23-0575
Key Facts
Patch immediately- CVE-2023-4966 is a high-severity vulnerability (CVSS 7.5 v3.1) affecting Netscaler Application Delivery Controller (Citrix), NetScaler Gateway (Citrix).
- It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Oct 17, 2023 and is known to be used in ransomware campaigns. Public exploit code is available.
- EPSS estimates a 100% probability of exploitation in the next 30 days.
- Fixed versions are available, including Netscaler Application Delivery Controller 12.1-55.300, Netscaler Application Delivery Controller 13.0-92.19, Netscaler Application Delivery Controller 13.1-37.164.
- Brandefense priority: patch immediately, because it is listed as exploited in the wild.
CVSS v3.1
7.5
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
EPSS (30-day exploit likelihood)
100%
Higher than 99.9% of all scored CVEs
Exploited in the wild
Yes
4 catalog listings, used by ransomware
Public exploit code
Available
Proof-of-concept or weaponized module
Get the full CVE-2023-4966 brief as a PDF
Every affected product and fixed release, exploitation status and a first 24 hours response checklist, emailed within minutes.
Description
Sensitive information disclosure in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.
Known-Exploited Catalog Listings
| Catalog | Added | Remediation due | Ransomware use |
|---|---|---|---|
| CISA KEV | Oct 18, 2023 | Nov 8, 2023 | Known |
| Industry KEV feed | Oct 17, 2023 | Nov 8, 2023 | Known |
| CIRCL KEV | Oct 18, 2023 | Nov 8, 2023 | Known |
| ENISA EUVD | Oct 18, 2023 | n/a | Not reported |
Required action: Apply mitigations and kill all active and persistent sessions per vendor instructions [https://www.netscaler.com/blog/news/cve-2023-4966-critical-security-update-now-available-for-netscaler-adc-and-netscaler-gateway/] OR discontinue use of the product if mitigations are unavailable.
Affected Products
6 affected entries in total| Product | Affected versions | Fixed in |
|---|---|---|
| Netscaler Application Delivery ControllerCitrix | >= 14.1 | 13.0-92.19 |
| NetScaler GatewayCitrix | >= 14.1 | 13.0-92.19 |
Patched Releases
Netscaler Application Delivery Controller
12.1-55.300, 13.0-92.19, 13.1-37.164, 13.1-49.15, 14.1-8.50, 37.164, 49.15, 55.300, 8.50, 92.19
NetScaler Gateway
13.0-92.19, 13.1-49.15, 14.1-8.50, 49.15, 8.50, 92.19
Timeline
Publicly disclosed
Oct 11, 2023
Added to Industry KEV feed
Oct 17, 2023
Added to CISA KEV
Oct 18, 2023
Added to CIRCL KEV
Oct 18, 2023
Added to ENISA EUVD
Oct 18, 2023
Last updated
Jul 31, 2026
Weakness Type
- CWE-119 Improper Restriction of Operations within the Bounds of a Memory Buffer
References
- advisoryhttp://packetstormsecurity.com/files/175323/Citrix-Bleed-Session-Token-Leakage-Proof-Of-Concept.html
- advisoryhttps://support.citrix.com/article/CTX575089/citrix-hypervisor-multiple-security-updates
- advisoryhttps://support.citrix.com/article/CTX579459
- advisoryhttps://www.bleepingcomputer.com/news/security/new-critical-citrix-netscaler-flaw-exposes-sensitive-data/
- advisoryUSOM advisory
FAQ
Common Questions.
Sensitive information disclosure in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.
Affected: Netscaler Application Delivery Controller (Citrix) versions >= 14.1; NetScaler Gateway (Citrix) versions >= 14.1. The full list is in the CVE brief.
It is exploited in the wild, listed in CISA KEV, Industry KEV feed, CIRCL KEV, ENISA EUVD since Oct 17, 2023 and is known to be used in ransomware campaigns.
Yes. It was added on Oct 18, 2023 with a federal remediation due date of Nov 8, 2023.
Public exploit code is available.
Fixed versions are available, including Netscaler Application Delivery Controller 12.1-55.300, Netscaler Application Delivery Controller 13.0-92.19, Netscaler Application Delivery Controller 13.1-37.164.
Brandefense priority: patch immediately, because it is listed as exploited in the wild.
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