{"id":"CVE-2021-35211","published":"2021-07-14T21:15:08Z","modified":"2026-06-17T03:57:18Z","title":"SolarWinds Serv-U Remote Code Execution Vulnerability","vendor":"SolarWinds","product":"Serv-U","tier":"core","eol":null,"description":{"text":"Microsoft discovered a remote code execution (RCE) vulnerability in the SolarWinds Serv-U product utilizing a Remote Memory Escape Vulnerability. If exploited, a threat actor may be able to gain privileged access to the machine hosting Serv-U Only. SolarWinds Serv-U Managed File Transfer and Serv-U Secure FTP for Windows before 15.2.3 HF2 are affected by this vulnerability.","provenance":"source","from":"NVD"},"summary":{"text":"The SolarWinds Serv-U product, specifically its Managed File Transfer and Secure FTP for Windows components, contains a remote memory escape flaw classified as an out-of-bounds write that enables remote code execution. An attacker with network access can exploit it without authentication or user interaction, potentially gaining privileged access to the machine hosting Serv-U, and this applies only to affected versions prior to 15.2.3 HF2.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-23T07:01:21Z"},"cvss":{"score":10.0,"severity":"CRITICAL","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H","provenance":"source","from":"NVD"},"epss":{"score":0.9116,"percentile":0.99808,"date":"2026-10-29","provenance":"source"},"kev":{"dateAdded":"2021-11-03","dueDate":"2021-11-17","ransomware":true,"requiredAction":"Apply updates per vendor instructions.","notes":"https://nvd.nist.gov/vuln/detail/CVE-2021-35211","provenance":"source"},"vulncheckKev":{"dateAdded":"2021-07-13","exploitedFirstSeen":"2021-07-13","ransomware":true,"evidence":[{"url":"https://www.microsoft.com/en-us/security/blog/2021/07/13/microsoft-discovers-threat-actor-targeting-solarwinds-serv-u-software-with-0-day-exploit/","date":"2021-07-13"},{"url":"https://www.crowdstrike.com/blog/how-falcon-complete-stopped-a-solarwinds-serv-u-exploit-campaign/","date":"2021-10-21"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2021-11-03"},{"url":"https://research.nccgroup.com/2021/11/08/ta505-exploits-solarwinds-serv-u-vulnerability-cve-2021-35211-for-initial-access","date":"2021-11-08"},{"url":"https://research.nccgroup.com/2021/11/08/ta505-exploits-solarwinds-serv-u-vulnerability-cve-2021-35211-for-initial-access/","date":"2021-11-08"},{"url":"https://cybersecurityworks.com/howdymanage/uploads/file/ransomware-_-2022-spotlight-report_compressed.pdf","date":"2022-01-26"},{"url":"https://cybersecurityworks.com/howdymanage/uploads/file/Spotlight%20Report%20-%20Index%20Update%20Q2%20-%20Q3%20-%20Final%20Version_compressed.pdf","date":"2022-05-18"},{"url":"https://www.ivanti.com/resources/v/doc/pr-survey-report/ransomware-quarterly-indexreport_q2-q3","date":"2022-10-21"},{"url":"https://query.prod.cms.rt.microsoft.com/cms/api/am/binary/RE5bUvv","date":"2022-11-07"},{"url":"https://fourcore.io/blogs/clop-ransomware-history-adversary-simulation","date":"2023-06-03"}],"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.microsoft.com/security/blog/2021/07/13/microsoft-discovers-threat-actor-targeting-solarwinds-serv-u-software-with-0-day-exploit","tags":["Patch","Vendor Advisory"]},{"url":"https://www.solarwinds.com/trust-center/security-advisories/cve-2021-35211","tags":["Patch","Vendor Advisory"]},{"url":"https://www.microsoft.com/security/blog/2021/07/13/microsoft-discovers-threat-actor-targeting-solarwinds-serv-u-software-with-0-day-exploit","tags":["Patch","Vendor Advisory"]},{"url":"https://www.solarwinds.com/trust-center/security-advisories/cve-2021-35211","tags":["Patch","Vendor Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-35211","tags":["US Government Resource"]}],"techniques":[{"id":"T1190","name":"Exploit Public-Facing Application","tactics":["initial-access"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Remote exploit of network-facing Serv-U service","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"remote code execution (RCE) vulnerability in the SolarWinds Serv-U product","start":23,"end":97}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1068","name":"Exploitation for Privilege Escalation","tactics":["privilege-escalation"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Gains privileged access on host","mappingType":"primary_impact","evidence":[{"from":"description","quote":"may be able to gain privileged access to the machine hosting Serv-U","start":175,"end":242}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-21854","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-21854","exploited":true,"exploitedSince":"2021-11-03","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":3,"skipped":0,"earliest":"2021-09-30","earliestUrl":"https://github.com/NattiSamson/Serv-U-CVE-2021-35211","repos":[{"name":"BishopFox/CVE-2021-35211","url":"https://github.com/BishopFox/CVE-2021-35211","stars":38,"created":"2022-01-14"},{"name":"NattiSamson/Serv-U-CVE-2021-35211","url":"https://github.com/NattiSamson/Serv-U-CVE-2021-35211","stars":12,"created":"2021-09-30"},{"name":"0xhaggis/CVE-2021-35211","url":"https://github.com/0xhaggis/CVE-2021-35211","stars":1,"created":"2021-10-24"}]},"nuclei":[{"id":"CVE-2021-35211","name":"SolarWinds Serv-U FTP - Remote Code 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