{"id":"CVE-2023-6549","kind":"vulnerability","aliases":["CVE-2023-6549"],"related":[],"title":"Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway…","description":"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.\n\nCISA required action: Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.","summary":"Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow that lets an attacker crash the appliance, causing denial of service. CISA lists it as actively exploited in the wild.","severity":"high","cvss":8.2,"epss":null,"exploited":true,"exploited_at":"2024-01-17T00:00:00+00:00","products":[{"name":"Citrix NetScaler ADC and NetScaler Gateway","fixed":[],"affected":"","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["12.1-55.302"],"affected":">= 12.1, < 12.1-55.302","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["13.0-92.21"],"affected":">= 13.0, < 13.0-92.21","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["13.1-37.176"],"affected":">= 13.1, < 13.1-37.176","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["13.1-51.15"],"affected":">= 13.1, < 13.1-51.15","ecosystem":"vendor"},{"name":"citrix netscaler application delivery controller","fixed":["14.1-12.35"],"affected":">= 14.1, < 14.1-12.35","ecosystem":"vendor"},{"name":"citrix netscaler gateway","fixed":["13.0-92.21"],"affected":">= 13.0, < 13.0-92.21","ecosystem":"vendor"},{"name":"citrix netscaler gateway","fixed":["13.1-51.15"],"affected":">= 13.1, < 13.1-51.15","ecosystem":"vendor"},{"name":"citrix netscaler gateway","fixed":["14.1-12.35"],"affected":">= 14.1, < 14.1-12.35","ecosystem":"vendor"}],"ecosystems":["vendor"],"tags":["citrix","exploited","infrastructure","netscaler","self-hosted","vpn-gateway"],"not_affected_if":["default-config"],"how_to_check":null,"fix":"Apply the mitigation or fixed build from Citrix's advisory for CVE-2023-6549; if none is available, discontinue use of the product as CISA directs.","status":"open","published_at":"2024-01-17T00:00:00+00:00","first_seen_at":"2026-10-23T19:11:51+00:00","triaged_at":"2026-10-23T21:02:28+00:00","updated_at":"2026-10-23T22:29:05+00:00","category":"infrastructure","confidence":0.6,"triage":{"at":"2026-10-23T21:02:28Z","model":"claude-haiku-5-5","output":{"fix":"Apply the mitigation or fixed build from Citrix's advisory for CVE-2023-6549; if none is available, discontinue use of the product as CISA directs.","reach":"internet","impact":"medium","summary":"Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow that lets an attacker crash the appliance, causing denial of service. CISA lists it as actively exploited in the wild.","category":"infrastructure","who_cares":["netscaler","citrix","self-hosted","vpn-gateway"],"confidence":0.6,"needs_auth":"unknown","worst_case":"Appliance crashes and stops serving VPN, ICA proxy, or AAA traffic.","analyst_note":"Get affected and fixed versions and the exact configuration triggers from the Citrix advisory (support.citrix.com) and the CISA KEV entry; sources here give none.","how_to_check":"unknown","needs_analyst":true,"not_affected_if":["default-config"],"user_interaction":"no","needs_special_setup":"yes","severity_if_unknown":"high"},"cost_usd":0.000479,"input_tokens":2896,"output_tokens":379,"severity_before":"unknown"},"analyst_status":null,"analyst_note":null,"search":"'-2023':19A,22A '-6549':20A,23A 'aaa':137C 'action':142C 'activ':99B 'adc':14A,26A,76B,106C 'allow':116C 'and':27A 'appli':143C 'applianc':90B 'application':32A,37A,42A,47A,52A 'attack':87B 'bound':7A 'buffer':11A,82B,112C 'caus':91B 'cisa':95B,140C 'citrix':24A,30A,35A,40A,45A,50A,55A,58A,61A,64B,74B,104C 'configur':124C 'contain':80B,110C 'controller':34A,39A,44A,49A,54A 'crash':88B 'cve':18A,21A 'cvpn':133C 'delivery':33A,38A,43A,48A,53A 'denial':92B,120C 'denial-of-servic':119C 'discontinu':149C 'exploit':65B,100B 'gateway':17A,29A,57A,60A,63A,73B,79B,109C,127C 'host':70B 'ica':131C 'improp':1A 'infrastructur':66B 'instruct':147C 'let':85B 'list':96B 'memori':10A 'mitig':144C,155C 'netscal':13A,16A,67B,75B,78B,105C,108C 'netscaler':25A,28A,31A,36A,41A,46A,51A,56A,59A,62A 'oper':4A 'overflow':83B,113C 'per':145C 'product':153C 'proxi':132C,135C 'rdp':134C 'requir':141C 'restrict':2A 'self':69B 'self-host':68B 'server':130C,139C 'servic':94B,122C 'unavail':157C 'use':150C 'vendor':146C 'virtual':129C,138C 'vpn':72B,128C 'vpn-gateway':71B 'vulner':114C 'wild':103B 'within':5A","nicknames":[],"mitigations":[],"who_affected":null,"tier":null,"verified":{},"analyst_revisit_at":null,"first_public_at":"2024-01-17T00:00:00+00:00","kev":{"dateAdded":"2024-01-17","dueDate":"2024-02-07","requiredAction":"Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.","knownRansomwareCampaignUse":"Unknown"},"cvss_vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:H","cvss_by":"secure@citrix.com","poc_count":0,"sources":[{"source":"kev","external_id":"CVE-2023-6549","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?search_api_fulltext=CVE-2023-6549","severity":null,"published_at":"2024-01-17T00:00:00+00:00","modified_at":null,"first_seen_at":"2026-10-23T19:11:51+00:00","fetched_at":"2026-10-25T14:39:39+00:00","note":null},{"source":"nvd","external_id":"CVE-2023-6549","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-6549","severity":null,"published_at":"2024-01-17T21:15:11+00:00","modified_at":"2026-06-17T06:50:58+00:00","first_seen_at":"2026-10-23T22:29:05+00:00","fetched_at":"2026-10-23T22:29:05+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"}