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CVE-2023-4966

98
FAUCET Score

CVE-2023-4966, widely referred to as Citrix Bleed, is a sensitive information disclosure vulnerability affecting Citrix NetScaler ADC and NetScaler Gateway appliances configured as Gateway or AAA virtual servers. This high-severity flaw allows unauthenticated remote attackers to exploit buffer errors via a low-complexity network attack, enabling the leakage of session tokens and subsequent session hijacking without user interaction. The vulnerability presents a critical risk as it is actively exploited in the wild by ransomware groups, is listed in the CISA KEV catalog, and has public exploit code available in common penetration testing frameworks like Metasploit and Nuclei.

Impacted Technologies

VendorProductVersion(s)CPE
>= 12.1, < 12.1-55.300CPE matchmatch criteria
cpe:2.3:a:citrix:netscaler_application_delivery_controller:*:*:*:*:fips:*:*:*
>= 12.1, < 12.1-55.300CPE matchmatch criteria
cpe:2.3:a:citrix:netscaler_application_delivery_controller:*:*:*:*:ndcpp:*:*:*
>= 13.0, < 13.0-92.19CPE matchmatch criteria
cpe:2.3:a:citrix:netscaler_application_delivery_controller:*:*:*:*:-:*:*:*
>= 13.1, < 13.1-37.164CPE matchmatch criteria
cpe:2.3:a:citrix:netscaler_application_delivery_controller:*:*:*:*:fips:*:*:*
>= 13.1, < 13.1-49.15CPE matchmatch criteria
cpe:2.3:a:citrix:netscaler_application_delivery_controller:*:*:*:*:-:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.4CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
LOW
Exploitability Score
3.9
Impact Score
5.5
CvssVersion
3.1

Exploit Intelligence

EPSS Score
100.00%
Probability of exploitation in next 30 days
EPSS Percentile
100.0%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Added to KEV · Oct 18, 2023
Metasploit: Citrix ADC (NetScaler) Bleed Scanner · Oct 25, 2023
Nuclei: CVE-2023-4966 · Oct 24, 2023
This CVE's current EPSS score of 1.0000 is in the 100th percentile among its peer group of 51,506 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.0 Reddit, 0.1 Bluesky, 0.1 Mastodon, and 0.4 GitHub mentions.

Media Mentions

The average CVE in this peer group has 0.1 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Vendor Patches (1)

citrixvendor investigatingvia nvd_reference
View patch

References

cisa.gov / known-exploited-vulnerabilities-catalog
US Government Resource
packetstormsecurity.com / files/175323/Citrix-Bleed-Session-Token-Leakage-Proof-Of-Concept.html
Third Party AdvisoryVDB Entry
support.citrix.com / article/CTX579459
Vendor Advisory