CVE-2023-4966

CRITICALNVD 7.59.4▲
EchelonGraph scoreHIGH confidence

Score elevated to 9.4 because this CVE is listed on the CISA Known Exploited Vulnerabilities catalog (added 2023-10-18), indicating real-world exploitation has been confirmed by US federal agencies. NVD baseline CVSS 7.5 retained for reference. Confidence: HIGH.

Triggered by: CISA KEV (actively exploited)
Sources: cisa_kev, epss, ghsa, nvd
Exploited in the wild
9.4EG
EchelonGraph verdictPatch nowTreat as an emergency — this is being exploited.
  • 3,400 internet-exposed hosts are running an affected version right now
  • Actively exploited in the wild (CISA-KEV)
  • Linked to ransomware campaigns
CISA-KEV: ExploitedEPSS PROB: 100%CVSS: 7.5Exploit: cisa kev · ssvc active · kev ransomware · Metasploit · epss top5pct · epss high · public exploitExposed: 3,400

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

Live · internet exposure

3,400 internet-exposed hosts are running an affected version of CVE-2023-4966 right now.

across 23 countries (Germany, Australia, United Kingdom, United States, Bulgaria)top: netscaler_gateway🔒 ransomware-linked
See the live KEV-Exposure radar →Found passively from public internet-scan data — aggregate, host-redacted.

EchelonGraph is the only CVE feed that fuses live vulnerability intelligence with its own live internet-exposure radar — so you see not just that a CVE is exploited, but how much of the internet is exposed to it right now.

CVSS v3
7.5
EG Score
9.4(high)
EG Risk
97(Act)
EG Risk 97/100SSVC: Act

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity94% × 45%
Exploitation100% × 40%
Automatability100% × 15%
Action: Fix now — active exploitation, automatable, high impact.
EPSS PROB
100%
EPSS %ILE
100%
KEV
⚠ Exploited

Published

October 10, 2023

Last Modified

July 31, 2026

Advisory Details (3)

Auto-updated Jun 1, 2026
⚠️ Active exploitation confirmed. Patch available. Sources: cisa.
cisa Patch Available🔴 Active Exploitation

Known Exploited Vulnerabilities Catalog | CISA

Known Exploited Vulnerabilities Catalog | CISA. Listed in CISA Known Exploited Vulnerabilities catalog.

https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-4966
generic

Loading...

https://support.citrix.com/article/CTX579459
generic

Packet Storm

http://packetstormsecurity.com/files/175323/Citrix-Bleed-Session-Token-Leakage-Proof-Of-Concept.html

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 48× in last 7d / 209× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 765 total refreshes for this CVE.

  1. 2026-09-19 04:52 UTCGHSA enrichment
  2. 2026-09-19 01:02 UTCGHSA enrichment
  3. 2026-09-18 21:13 UTCGHSA enrichment
  4. 2026-09-18 19:20 UTCCISA KEV update
  5. 2026-09-18 17:24 UTCGHSA enrichment
  6. 2026-09-18 14:15 UTCCISA KEV update
  7. 2026-09-18 13:35 UTCGHSA enrichment
  8. 2026-09-18 09:46 UTCGHSA enrichment
  9. 2026-09-18 05:56 UTCGHSA enrichment
  10. 2026-09-18 02:08 UTCGHSA enrichment
  11. 2026-09-17 22:19 UTCGHSA enrichment
  12. 2026-09-17 18:30 UTCGHSA enrichment
  13. 2026-09-17 14:41 UTCGHSA enrichment
  14. 2026-09-17 10:52 UTCGHSA enrichment
  15. 2026-09-17 07:03 UTCGHSA enrichment
  16. 2026-09-17 03:14 UTCGHSA enrichment
  17. 2026-09-16 23:25 UTCGHSA enrichment
  18. 2026-09-16 19:36 UTCGHSA enrichment
  19. 2026-09-16 15:47 UTCGHSA enrichment
  20. 2026-09-16 14:10 UTCCISA KEV update
  21. 2026-09-16 11:58 UTCGHSA enrichment
  22. 2026-09-16 08:09 UTCGHSA enrichment
  23. 2026-09-16 04:18 UTCGHSA enrichment
  24. 2026-09-16 00:27 UTCGHSA enrichment
  25. 2026-09-15 20:36 UTCGHSA enrichment
Show 75 more
  1. 2026-09-15 16:40 UTCGHSA enrichment
  2. 2026-09-15 12:51 UTCGHSA enrichment
  3. 2026-09-15 09:02 UTCGHSA enrichment
  4. 2026-09-15 05:13 UTCGHSA enrichment
  5. 2026-09-15 01:20 UTCGHSA enrichment
  6. 2026-09-14 21:31 UTCGHSA enrichment
  7. 2026-09-14 19:24 UTCCISA KEV update
  8. 2026-09-14 17:42 UTCGHSA enrichment
  9. 2026-09-14 13:53 UTCGHSA enrichment
  10. 2026-09-14 10:04 UTCGHSA enrichment
  11. 2026-09-14 06:15 UTCGHSA enrichment
  12. 2026-09-14 02:26 UTCGHSA enrichment
  13. 2026-09-13 22:36 UTCGHSA enrichment
  14. 2026-09-13 18:47 UTCGHSA enrichment
  15. 2026-09-13 14:58 UTCGHSA enrichment
  16. 2026-09-13 11:09 UTCGHSA enrichment
  17. 2026-09-13 07:19 UTCGHSA enrichment
  18. 2026-09-13 03:31 UTCGHSA enrichment
  19. 2026-09-12 23:42 UTCGHSA enrichment
  20. 2026-09-12 19:53 UTCGHSA enrichment
  21. 2026-09-12 16:04 UTCGHSA enrichment
  22. 2026-09-12 12:15 UTCGHSA enrichment
  23. 2026-09-12 08:25 UTCGHSA enrichment
  24. 2026-09-12 04:36 UTCGHSA enrichment
  25. 2026-09-12 00:47 UTCGHSA enrichment
  26. 2026-09-11 20:58 UTCGHSA enrichment
  27. 2026-09-11 18:49 UTCCISA KEV update
  28. 2026-09-11 17:09 UTCGHSA enrichment
  29. 2026-09-11 13:20 UTCGHSA enrichment
  30. 2026-09-11 09:31 UTCGHSA enrichment
  31. 2026-09-11 05:42 UTCGHSA enrichment
  32. 2026-09-11 01:53 UTCGHSA enrichment
  33. 2026-09-10 22:04 UTCGHSA enrichment
  34. 2026-09-10 19:28 UTCCISA KEV update
  35. 2026-09-10 18:14 UTCGHSA enrichment
  36. 2026-09-10 14:24 UTCGHSA enrichment
  37. 2026-09-10 10:35 UTCGHSA enrichment
  38. 2026-09-10 06:44 UTCGHSA enrichment
  39. 2026-09-10 02:55 UTCGHSA enrichment
  40. 2026-09-09 23:05 UTCGHSA enrichment
  41. 2026-09-09 19:16 UTCGHSA enrichment
  42. 2026-09-09 19:08 UTCCISA KEV update
  43. 2026-09-09 15:26 UTCGHSA enrichment
  44. 2026-09-09 11:37 UTCGHSA enrichment
  45. 2026-09-09 07:47 UTCGHSA enrichment
  46. 2026-09-09 03:58 UTCGHSA enrichment
  47. 2026-09-09 00:09 UTCGHSA enrichment
  48. 2026-09-08 20:20 UTCGHSA enrichment
  49. 2026-09-08 18:54 UTCCISA KEV update
  50. 2026-09-08 16:31 UTCGHSA enrichment
  51. 2026-09-08 12:39 UTCGHSA enrichment
  52. 2026-09-08 08:47 UTCGHSA enrichment
  53. 2026-09-08 04:58 UTCGHSA enrichment
  54. 2026-09-08 01:08 UTCGHSA enrichment
  55. 2026-09-07 21:19 UTCGHSA enrichment
  56. 2026-09-07 17:30 UTCGHSA enrichment
  57. 2026-09-07 13:40 UTCGHSA enrichment
  58. 2026-09-07 09:48 UTCGHSA enrichment
  59. 2026-09-07 05:59 UTCGHSA enrichment
  60. 2026-09-07 02:10 UTCGHSA enrichment
  61. 2026-09-06 22:18 UTCGHSA enrichment
  62. 2026-09-06 18:28 UTCGHSA enrichment
  63. 2026-09-06 14:39 UTCGHSA enrichment
  64. 2026-09-06 10:49 UTCGHSA enrichment
  65. 2026-09-06 07:00 UTCGHSA enrichment
  66. 2026-09-06 03:11 UTCGHSA enrichment
  67. 2026-09-05 23:22 UTCGHSA enrichment
  68. 2026-09-05 19:32 UTCGHSA enrichment
  69. 2026-09-05 15:43 UTCGHSA enrichment
  70. 2026-09-05 11:54 UTCGHSA enrichment
  71. 2026-09-05 08:03 UTCGHSA enrichment
  72. 2026-09-05 04:14 UTCGHSA enrichment
  73. 2026-09-05 00:24 UTCGHSA enrichment
  74. 2026-09-04 20:35 UTCGHSA enrichment
  75. 2026-09-04 17:38 UTCCISA KEV update

Publicly available exploits

(9 references)

Working exploit code is in the public domain (1 Metasploit module) (7 GitHub PoCs). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCmorganwdavis/overread
    First seen Dec 16, 2023

    Simulates CVE-2023-4966 Citrix Bleed overread bug

    Open source ↗
  • GitHub PoCRevoltSecurities/CVE-2023-4966
    First seen Oct 29, 2023

    An Exploitation script developed to exploit the CVE-2023-4966 bleed citrix information disclosure vulnerability

    Open source ↗
  • GitHub PoCcertat/citrix-logchecker
    First seen Oct 28, 2023

    Parse citrix netscaler logs to check for signs of CVE-2023-4966 exploitation

    Open source ↗
  • GitHub PoCdinosn/citrix_cve-2023-4966
    First seen Oct 25, 2023

    Citrix CVE-2023-4966 from assetnote modified for parallel and file handling

    Open source ↗
  • GitHub PoCassetnote/exploits/CVE-2023-4966✓ verified
    First seen Oct 25, 2023

    Assetnote PoC for session-token extraction from vulnerable NetScaler appliances.

    Open source ↗
  • GitHub PoCmlynchcogent/CVE-2023-4966-POC
    First seen Oct 25, 2023

    Proof Of Concept for te NetScaler Vuln

    Open source ↗
  • Metasploitauxiliary/scanner/http/citrix_bleed_cve_2023_4966✓ verified
    First seen Oct 25, 2023

    Citrix ADC (NetScaler) Bleed Scanner

    Open source ↗
  • GitHub PoCChocapikk/CVE-2023-4966
    First seen Oct 24, 2023

    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.

    Open source ↗
  • Nucleihttp/cves/2023/CVE-2023-4966.yaml
    First seen Jan 1, 2023

    Citrix Bleed - Leaking Session Tokens

    Open source ↗

Past incidents using this CVE

(1)

This CVE was central to one or more publicly-documented breaches. Each card links to authoritative reporting at the time of the incident.

  • Citrix Bleed (NetScaler)Oct 2023

    NetScaler ADC/Gateway buffer over-read leaked session tokens, letting attackers bypass MFA. Exploited by ransomware groups (LockBit, Medusa) against Boeing, ICBC, and Comcast within weeks of disclosure.

    Source: BleepingComputer

Related CVEs(same CWE)

Frequently asked(6)

What is CVE-2023-4966?
CVE-2023-4966 is a critical vulnerability published on October 10, 2023. 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.
When was CVE-2023-4966 disclosed?
CVE-2023-4966 was first published in the National Vulnerability Database on October 10, 2023, with the most recent update on July 31, 2026. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2023-4966 actively exploited?
Yes. CISA added CVE-2023-4966 to the Known Exploited Vulnerabilities catalog on October 18, 2023, affecting Citrix NetScaler ADC and NetScaler Gateway. KEV listing indicates confirmed exploitation in the wild; this CVE warrants immediate patching attention.
What is the CVSS score of CVE-2023-4966?
CVE-2023-4966 has a CVSS v3 base score of 7.5 (NVD). EchelonGraph synthesises NVD + CISA KEV + FIRST EPSS + GHSA into a combined EG score of 9.4.
Which products are affected by CVE-2023-4966?
CVE-2023-4966 affects Citrix NetScaler ADC and NetScaler Gateway. The full affected-products list, including version ranges and fixed versions, is shown in the Affected Packages section of this page.
How do I remediate CVE-2023-4966?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2023-4966, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

Explore the affected products and dependency analysis for CVE-2023-4966

Explore →

Is Your Infrastructure Affected by CVE-2023-4966?

EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.

Start Free Scan →Browse All CVEs