{"id":"CVE-2023-6549","published":"2024-01-17T21:15:11Z","modified":"2026-06-17T06:50:58Z","title":"Citrix NetScaler ADC and NetScaler Gateway Buffer Overflow Vulnerability","vendor":"Citrix","product":"NetScaler ADC and NetScaler Gateway","tier":"core","eol":null,"description":{"text":"Improper Restriction of Operations within the Bounds of a Memory Buffer in NetScaler ADC and NetScaler Gateway allows Unauthenticated Denial of Service and Out-Of-Bounds Memory Read","provenance":"source","from":"NVD"},"summary":{"text":"Citrix NetScaler ADC and NetScaler Gateway contain a buffer overflow flaw (improper restriction of operations within the bounds of a memory buffer) that allows out-of-bounds memory reads. An unauthenticated remote attacker with network access can trigger a denial of service, requiring no authentication, no user interaction, and only low complexity.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:13:17Z"},"cvss":{"score":7.5,"severity":"HIGH","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.57633,"percentile":0.99081,"date":"2026-10-29","provenance":"source"},"kev":{"dateAdded":"2024-01-17","dueDate":"2024-02-07","ransomware":false,"requiredAction":"Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.","notes":"https://support.citrix.com/article/CTX584986/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20236548-and-cve20236549;   https://nvd.nist.gov/vuln/detail/CVE-2023-6549","provenance":"source"},"vulncheckKev":{"dateAdded":"2024-01-16","exploitedFirstSeen":"2024-01-16","ransomware":false,"evidence":[{"url":"https://support.citrix.com/article/CTX584986/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20236548-and-cve20236549","date":"2024-01-16"},{"url":"https://www.tenable.com/blog/cve-2023-6548-cve-2023-6549-zero-day-vulnerabilities-netscaler-adc-gateway-exploited","date":"2024-01-16"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2024-01-17"},{"url":"https://redsense.com/publications/yearly-intel-trend-review-2023/","date":"2024-01-30"},{"url":"https://www.cert.europa.eu/publications/threat-intelligence/tlr2024/pdf","date":"2025-02-25"},{"url":"https://www.tenable.com/blog/verizon-2025-dbir-tenable-research-collaboration","date":"2025-04-23"},{"url":"https://www.verizon.com/business/resources/T32e/reports/2025-dbir-data-breach-investigations-report.pdf","date":"2025-04-25"},{"url":"https://dashboard.shadowserver.org/statistics/honeypot/vulnerability/map/?day=2025-07-02&host_type=src&vulnerability=cve-2023-6549","date":"2025-07-02"},{"url":"https://dashboard.shadowserver.org/statistics/honeypot/vulnerability/map/?day=2025-07-03&host_type=src&vulnerability=cve-2023-6549","date":"2025-07-03"},{"url":"https://dashboard.shadowserver.org/statistics/honeypot/vulnerability/map/?day=2025-07-04&host_type=src&vulnerability=cve-2023-6549","date":"2025-07-04"}],"evidenceTotal":18,"provenance":"source"},"exploited":true,"otx":{"pulseCount":50,"pulses":[{"name":"Actively_Exploited_Kev | Oct 30, 2026","url":"https://otx.alienvault.com/pulse/6ae35d889ea92b4ce19c2680","created":"2026-10-29"},{"name":"Actively_Exploited_Kev | Oct 29, 2026","url":"https://otx.alienvault.com/pulse/6ae20c1db17e7057ae7d9ad1","created":"2026-10-28"},{"name":"Actively_Exploited_Kev | Oct 28, 2026","url":"https://otx.alienvault.com/pulse/6ae0ba7e0e2a97ff7b218819","created":"2026-10-27"},{"name":"Actively_Exploited_Kev | Oct 27, 2026","url":"https://otx.alienvault.com/pulse/6adf68b85c3e852f3c111d18","created":"2026-10-26"},{"name":"Actively_Exploited_Kev | Oct 24, 2026","url":"https://otx.alienvault.com/pulse/6adb740e397c3ad4799aa4cd","created":"2026-10-23"},{"name":"Actively_Exploited_Kev | Oct 23, 2026","url":"https://otx.alienvault.com/pulse/6ada236fcfba2dfa730ea482","created":"2026-10-22"},{"name":"Actively_Exploited_Kev | Oct 22, 2026","url":"https://otx.alienvault.com/pulse/6ad8d33a077cbb5cab524d80","created":"2026-10-21"},{"name":"Actively_Exploited_Kev | Oct 21, 2026","url":"https://otx.alienvault.com/pulse/6ad78130c4d1ac2be83a8b6d","created":"2026-10-20"},{"name":"Actively_Exploited_Kev | Oct 20, 2026","url":"https://otx.alienvault.com/pulse/6ad62f63c24a405a3423cc13","created":"2026-10-19"},{"name":"Actively_Exploited_Kev | Oct 19, 2026","url":"https://otx.alienvault.com/pulse/6ad4dda174e5797d0bd238b7","created":"2026-10-18"}],"provenance":"machine"},"cwes":[{"id":"CWE-119","name":"Improper Restriction of Operations within the Bounds of a Memory Buffer"}],"references":[{"url":"https://support.citrix.com/article/CTX584986/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20236548-and-cve20236549","tags":["Vendor Advisory"]},{"url":"https://support.citrix.com/article/CTX584986/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20236548-and-cve20236549","tags":["Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-6549","tags":["US Government Resource"]}],"techniques":[{"id":"T1574","name":"Hijack Execution Flow","tactics":["execution","stealth"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Buffer Overflow","mappingType":"exploitation_technique","evidence":[],"comment":"This buffer overflow vulnerability can be exploited to cause a denial of service.","confidence":"high"},{"id":"T1499","name":"Endpoint Denial of Service","tactics":["impact"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Buffer Overflow","mappingType":"primary_impact","evidence":[],"comment":"This buffer overflow vulnerability can be exploited to cause a denial of service.","confidence":"high"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2023-58779","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2023-58779","exploited":true,"exploitedSince":"2024-01-17","provenance":"source"},"exploits":[],"exploitSources":{"nuclei":[{"id":"CVE-2023-6549","name":"Citrix Netscaler ADC & Gateway - Out-Of-Bounds Memory Read","severity":"critical","path":"http/cves/2023/CVE-2023-6549.yaml","url":"https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2023/CVE-2023-6549.yaml"}],"provenance":"source"},"exploitRefs":[],"flow":[{"stage":"exploitation","techniques":["T1574"],"provenance":"source"},{"stage":"primary","techniques":["T1499"],"provenance":"source"}],"timeline":[{"date":"2024-01-16","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://support.citrix.com/article/CTX584986/netscaler-adc-and-netscaler-gateway-security-bulletin-for-cve20236548-and-cve20236549","provenance":"source"},{"date":"2024-01-17","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-6549","provenance":"source"},{"date":"2024-01-17","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2024-01-17","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2023-58779","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":0},"priority":{"score":68.1,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":0.0,"detail":"added 1018 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.82,"detail":"percentile 0.9908"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"1 nuclei template"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"50 pulses"},{"name":"CVSS severity","points":5.25,"detail":"base score 7.5"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]},"lineage":{"familyId":"fam-class-citrix-netscaler-adc-and-netscaler-gateway-cwe-119"}}