{"id":"CVE-2023-4966","kind":"vulnerability","aliases":["CVE-2023-4966"],"related":[],"title":"Sensitive information disclosure in NetScaler ADC and NetScaler Gateway when configured as a Gateway (VPN virtual…","description":"Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow vulnerability that allows for sensitive information disclosure when configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server.\n\nCISA 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.","summary":"Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow when configured as a Gateway or AAA virtual server, leaking sensitive information from memory. Attackers can steal session tokens and bypass authentication, and the flaw is actively exploited in the wild per CISA KEV.","severity":"critical","cvss":9.4,"epss":null,"exploited":true,"exploited_at":"2023-10-18T00:00:00+00:00","products":[{"name":"Citrix NetScaler ADC and NetScaler Gateway","fixed":[],"affected":"","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["12.1-55.300"],"affected":">= 12.1, < 12.1-55.300","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["13.0-92.19"],"affected":">= 13.0, < 13.0-92.19","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["13.1-37.164"],"affected":">= 13.1, < 13.1-37.164","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["13.1-49.15"],"affected":">= 13.1, < 13.1-49.15","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["14.1-8.50"],"affected":">= 14.1, < 14.1-8.50","ecosystem":"vendor"},{"name":"citrix netscaler gateway","fixed":["13.0-92.19"],"affected":">= 13.0, < 13.0-92.19","ecosystem":"vendor"},{"name":"citrix netscaler gateway","fixed":["13.1-49.15"],"affected":">= 13.1, < 13.1-49.15","ecosystem":"vendor"},{"name":"citrix netscaler gateway","fixed":["14.1-8.50"],"affected":">= 14.1, < 14.1-8.50","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["citrix","exploited","gateway","netscaler","ransomware","self-hosted","vendor","vpn"],"not_affected_if":["no-aaa-vserver","not-gateway-config"],"how_to_check":"Check whether the appliance is configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server; sources do not give a specific command.","fix":"Apply the Citrix mitigations and kill all active and persistent sessions per the vendor advisory at 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.\nUpgrade to the fixed NetScaler build named in the Citrix advisory (version not stated in sources).","status":"open","published_at":"2023-10-10T14:15:10+00:00","first_seen_at":"2026-10-23T19:11:51+00:00","triaged_at":"2026-10-23T21:04:24+00:00","updated_at":"2026-10-23T22:29:04+00:00","category":"vendor","confidence":0.8,"triage":{"at":"2026-10-23T21:04:24Z","model":"claude-haiku-5-5","output":{"fix":"Apply the Citrix mitigations and kill all active and persistent sessions per the vendor advisory at 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.\nUpgrade to the fixed NetScaler build named in the Citrix advisory (version not stated in sources).","reach":"internet","impact":"high","summary":"Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow when configured as a Gateway or AAA virtual server, leaking sensitive information from memory. Attackers can steal session tokens and bypass authentication, and the flaw is actively exploited in the wild per CISA KEV.","category":"vendor","who_cares":["netscaler","citrix","self-hosted","vpn","gateway"],"confidence":0.8,"needs_auth":"no","worst_case":"Attacker reads sensitive memory, stealing session tokens and bypassing login","analyst_note":"Confirm affected and fixed versions and exact mitigation steps from the Citrix advisory linked in the CISA entry; sources do not state them.","how_to_check":"Check whether the appliance is configured as a Gateway (VPN virtual server, ICA Proxy, CVPN, RDP Proxy) or AAA virtual server; sources do not give a specific command.\nunknown\nunknown","needs_analyst":true,"not_affected_if":["not-gateway-config","no-aaa-vserver"],"user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"critical"},"cost_usd":0.000586,"input_tokens":2975,"output_tokens":578,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2023':18A,21A '-4966':19A,22A '/blog/news/cve-2023-4966-critical-security-update-now-available-for-netscaler-adc-and-netscaler-gateway/]':168C 'aaa':89B,148C 'action':153C 'activ':109B,159C 'adc':6A,25A,75B,119C 'allow':129C 'and':26A 'appli':154C 'application':31A,36A,41A,46A,51A 'attack':97B 'authent':104B 'buffer':81B,125C 'bypass':103B 'cisa':115B,151C 'citrix':23A,29A,34A,39A,44A,49A,54A,57A,60A,63B,73B,117C 'configur':11A,84B,135C 'contain':79B,123C 'controller':33A,38A,43A,48A,53A 'cve':17A,20A 'cvpn':144C 'delivery':32A,37A,42A,47A,52A 'disclosur':3A,133C 'discontinu':170C 'exploit':64B,110B 'flaw':107B 'gateway':9A,14A,28A,56A,59A,62A,65B,78B,87B,122C,138C 'host':70B 'ica':142C 'inform':2A,94B,132C 'instruct':165C 'kev':116B 'kill':157C 'leak':92B 'memori':96B 'mitig':155C,176C 'netscal':5A,8A,66B,74B,77B,118C,121C 'netscaler':24A,27A,30A,35A,40A,45A,50A,55A,58A,61A 'overflow':82B,126C 'per':114B,163C 'persist':161C 'product':174C 'proxi':143C,146C 'ransomwar':67B 'rdp':145C 'requir':152C 'self':69B 'self-host':68B 'sensit':1A,93B,131C 'server':91B,141C,150C 'session':100B,162C 'steal':99B 'token':101B 'unavail':178C 'use':171C 'vendor':71B,164C 'virtual':16A,90B,140C,149C 'vpn':15A,72B,139C 'vulner':127C 'wild':113B 'www.netscaler.com':167C 'www.netscaler.com/blog/news/cve-2023-4966-critical-security-update-now-available-for-netscaler-adc-and-netscaler-gateway/]':166C","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2023-10-10T14:15:10+00:00","kev":{"dateAdded":"2023-10-18","dueDate":"2023-11-08","requiredAction":"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.","knownRansomwareCampaignUse":"Known"},"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L","cvss_by":"secure@citrix.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2023-4966","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2023-4966","severity":null,"published_at":"2023-10-18T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:51+00:00","fetched_at":"2026-10-25T17:39:56+00:00","note":null},{"source":"nvd","external_id":"CVE-2023-4966","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-4966","severity":null,"published_at":"2023-10-10T14:15:10+00:00","modified_at":"2026-07-31T04:16:44+00:00","first_seen_at":"2026-10-23T22:29:04+00:00","fetched_at":"2026-10-23T22:29:04+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}