{"id":"CVE-2023-34048","published":"2023-10-25T18:17:27Z","modified":"2026-06-17T06:02:47Z","title":"VMware vCenter Server Out-of-Bounds Write Vulnerability","vendor":"VMware","product":"vCenter Server","tier":"core","eol":null,"description":{"text":"vCenter Server contains an out-of-bounds write vulnerability in the implementation of the DCERPC protocol. A malicious actor with network access to vCenter Server may trigger an out-of-bounds write potentially leading to remote code execution.","provenance":"source","from":"NVD"},"summary":{"text":"VMware vCenter Server contains an out-of-bounds write flaw in its implementation of the DCERPC protocol. The vulnerable code sits in the vCenter Server product itself, within the protocol handling component. An attacker with network access to vCenter Server, requiring no authentication and no user interaction, can trigger the out-of-bounds write, which could lead to remote code execution.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:03:13Z"},"cvss":{"score":9.8,"severity":"CRITICAL","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.99234,"percentile":0.99936,"date":"2026-10-29","provenance":"source"},"kev":{"dateAdded":"2024-01-22","dueDate":"2024-02-12","ransomware":false,"requiredAction":"Apply mitigations per vendor instructions or discontinue use of the product if mitigations are unavailable.","notes":"https://www.vmware.com/security/advisories/VMSA-2023-0023.html;  https://nvd.nist.gov/vuln/detail/CVE-2023-34048","provenance":"source"},"vulncheckKev":{"dateAdded":"2024-01-17","exploitedFirstSeen":"2024-01-17","ransomware":false,"evidence":[{"url":"https://www.vmware.com/security/advisories/VMSA-2023-0023.html","date":"2024-01-17"},{"url":"https://www.mandiant.com/resources/blog/chinese-vmware-exploitation-since-2021","date":"2024-01-18"},{"url":"https://www.rapid7.com/blog/post/2024/01/19/etr-critical-cves-in-outdated-versions-of-atlassian-confluence-and-vmware-vcenter-server/","date":"2024-01-19"},{"url":"https://censys.com/cve-2023-34048-vmware-vcenter/","date":"2024-01-22"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2024-01-22"},{"url":"https://www.sentinelone.com/resources/watchtower-end-of-year-report-2023/","date":"2024-01-31"},{"url":"https://storage.googleapis.com/gweb-uniblog-publish-prod/documents/Year_in_Review_of_ZeroDays.pdf","date":"2024-03-27"},{"url":"https://www.rapid7.com/globalassets/_pdfs/research/rapid7_2024_attack_intelligence_report.pdf","date":"2024-05-21"},{"url":"https://cloud.google.com/blog/topics/threat-intelligence/uncovering-unc3886-espionage-operations","date":"2024-06-18"},{"url":"https://www4.orangecyberdefense.com/security-navigator-2025-en","date":"2024-12-05"}],"evidenceTotal":21,"provenance":"source"},"exploited":true,"otx":{"pulseCount":50,"pulses":[{"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"},{"name":"Actively_Exploited_Kev | Oct 18, 2026","url":"https://otx.alienvault.com/pulse/6ad38c22e1848f8189d1c121","created":"2026-10-17"}],"provenance":"machine"},"cwes":[{"id":"CWE-787","name":"Out-of-bounds Write"}],"references":[{"url":"https://www.vmware.com/security/advisories/VMSA-2023-0023.html","tags":["Vendor Advisory"]},{"url":"https://www.vicarius.io/vsociety/posts/understanding-cve-2023-34048-a-zero-day-out-of-bound-write-in-vcenter-server","tags":["Exploit","Third Party Advisory"]},{"url":"https://www.vmware.com/security/advisories/VMSA-2023-0023.html","tags":["Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2023-34048","tags":["US Government Resource"]}],"techniques":[{"id":"T1203","name":"Exploitation for Client Execution","tactics":["execution"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Out-of-Bounds (Read and Write)","mappingType":"primary_impact","evidence":[],"comment":"This vulnerability is exploited by an adversary who has already gained network access to the vCenter Server. The adversary sends a crafted payload to the server that has a vulnerable DCERPC protocol and causes an out-of-bounds write on the jmp rax instruction. Adversary group UNC3886 has been attributed to leveraging this vulnerability in the wild to establish a backdoor in victim vCenter servers. ","confidence":"low","confidenceNote":"server-side bug exploitable without user interaction; client-execution technique does not fit"},{"id":"T1588.001","name":"Malware","tactics":["resource-development"],"provenance":"source","basis":"ctid-kev","bases":["ctid-kev"],"basisDetail":"CTID Mappings Explorer KEV 07/28/2025 (ATT&CK 16.1); capability: Out-of-Bounds (Read and Write)","mappingType":"secondary_impact","evidence":[],"comment":"This vulnerability is exploited by an adversary who has already gained network access to the vCenter Server. The adversary sends a crafted payload to the server that has a vulnerable DCERPC protocol and causes an out-of-bounds write on the jmp rax instruction. Adversary group UNC3886 has been attributed to leveraging this vulnerability in the wild to establish a backdoor in victim vCenter servers. ","confidence":"high"}],"reports":[{"id":"SRC-d520834e84b63932946c","title":"Cloaked and Covert: Uncovering UNC3886 Espionage Operations","publisher":"cloud.google.com","url":"https://cloud.google.com/blog/topics/threat-intelligence/uncovering-unc3886-espionage-operations","date":null,"mentions":[{"quote":"In January 2024, Mandiant published a blog post detailing UNC3886's activities exploiting CVE-2023-34048 (VMware vCenter) since late 2021.","start":2555,"end":2693},{"quote":"CVE-2023-34048 was not the only zero-day vulnerability exploited by UNC3886 during these intrusions.","start":2902,"end":3002}]}],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2023-38166","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2023-38166","exploited":true,"exploitedSince":"2024-01-22","provenance":"source"},"exploits":[],"exploitSources":{"nuclei":[{"id":"CVE-2023-34048","name":"VMware vCenter Server - Out-of-Bounds Write","severity":"critical","path":"http/cves/2023/CVE-2023-34048.yaml","url":"https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2023/CVE-2023-34048.yaml"}],"provenance":"source"},"exploitRefs":["https://www.vicarius.io/vsociety/posts/understanding-cve-2023-34048-a-zero-day-out-of-bound-write-in-vcenter-server"],"flow":[{"stage":"secondary","techniques":["T1588.001"],"provenance":"source"},{"stage":"related","techniques":["T1203"],"provenance":"source","lowConfidence":true}],"timeline":[{"date":"2023-10-25","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2023-34048","provenance":"source"},{"date":"2024-01-17","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://www.vmware.com/security/advisories/VMSA-2023-0023.html","provenance":"source"},{"date":"2024-01-22","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2024-01-22","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2023-38166","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":89},"priority":{"score":73.7,"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 1016 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.99,"detail":"percentile 0.9994"},{"name":"Named in threat reports","points":3.87,"detail":"1 report"},{"name":"Public exploit code","points":5.0,"detail":"1 NVD reference tagged Exploit; 1 nuclei template"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"50 pulses"},{"name":"CVSS severity","points":6.86,"detail":"base score 9.8"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]}}