{"id":"CVE-2021-3199","published":"2021-01-26T18:16:28Z","modified":"2026-10-09T14:20:47Z","title":"ONLYOFFICE Docs Server Path Traversal Vulnerability","vendor":"ONLYOFFICE","product":"Docs","tier":"core","eol":null,"description":{"text":"Directory traversal with remote code execution can occur in /upload in ONLYOFFICE Document Server before 5.6.3, when JWT is used, via a /.. sequence in an image upload parameter.","provenance":"source","from":"NVD"},"summary":{"text":"The path traversal flaw lives in the /upload endpoint of ONLYOFFICE Docs (Document Server) before 5.6.3, where a \"/..\" sequence in an image upload parameter is not properly restricted to the intended directory. An attacker can exploit it to achieve directory traversal and remote code execution over the network without authentication or user interaction, provided that JWT is enabled on the server.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-29T07:53:49Z"},"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":0.30244,"percentile":0.98217,"date":"2026-10-29","provenance":"source"},"kev":{"dateAdded":"2026-10-08","dueDate":"2026-10-11","ransomware":false,"requiredAction":"Apply mitigations in accordance with vendor instructions, ensuring compliance with CISA’s BOD 26-04 Prioritizing Security Updates Based on Risk (see URL in Notes) guidance and CISA’s “Forensics Triage Requirements” (see URL in Notes). Follow applicable BOD 26-04 guidance for cloud services or discontinue use of the product if mitigations are unavailable. Stakeholders are responsible for evaluating each asset's internet exposure and ensuring adherence to BOD 26-04 patching guidelines.","notes":"This vulnerability could affect an open-source component, third-party library, protocol, or proprietary implementation that could be used by different products. For more information, please see: ; https://github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md#563 ; BOD 26-04: https://www.cisa.gov/news-events/directives/bod-26-04-prioritizing-security-updates-based-risk ; Forensics Triage Requirements: https://www.cisa.gov/news-events/directives/bod-26-04-implementation-guidance-prioritizing-security-updates-based-risk ; https://nvd.nist.gov/vuln/detail/CVE-2021-3199","provenance":"source"},"vulncheckKev":{"dateAdded":"2026-10-08","exploitedFirstSeen":"2026-10-08","ransomware":false,"evidence":[{"url":"https://www.cisa.gov/news-events/cybersecurity-advisories/aa26-281a","date":"2026-10-08"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2026-10-08"}],"evidenceTotal":2,"provenance":"source"},"exploited":true,"otx":{"pulseCount":25,"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-22","name":"Improper Limitation of a Pathname to a Restricted Directory"}],"references":[{"url":"https://github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md#563","tags":["Release Notes","Third Party Advisory"]},{"url":"https://github.com/moehw/poc_exploits/tree/master/CVE-2021-3199/poc_uploadImageFile.py","tags":["Exploit","Third Party Advisory"]},{"url":"https://github.com/nola-milkin/poc_exploits/blob/master/CVE-2021-3199/poc_uploadImageFile.py","tags":["Exploit","Third Party Advisory"]},{"url":"https://github.com/ONLYOFFICE/DocumentServer/blob/903fe5ab7a275bd69c3c3346af2d21cf87ebeabf/CHANGELOG.md#563","tags":["Release Notes","Third Party Advisory"]},{"url":"https://github.com/moehw/poc_exploits/tree/master/CVE-2021-3199/poc_uploadImageFile.py","tags":["Exploit","Third Party Advisory"]},{"url":"https://github.com/nola-milkin/poc_exploits/blob/master/CVE-2021-3199/poc_uploadImageFile.py","tags":["Exploit","Third Party Advisory"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-3199","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 public-facing upload endpoint","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"Directory traversal with remote code execution can occur in /upload in ONLYOFFICE Document Server","start":0,"end":97}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"},{"id":"T1059","name":"Command and Scripting Interpreter","tactics":["execution"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Traversal enables code execution on server","mappingType":"primary_impact","evidence":[{"from":"description","quote":"Directory traversal with remote code execution can occur","start":0,"end":56}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2021-26539","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-26539","exploited":true,"exploitedSince":"2026-10-08","provenance":"source"},"exploits":[],"exploitSources":null,"exploitRefs":["https://github.com/moehw/poc_exploits/tree/master/CVE-2021-3199/poc_uploadImageFile.py","https://github.com/nola-milkin/poc_exploits/blob/master/CVE-2021-3199/poc_uploadImageFile.py"],"flow":[{"stage":"exploitation","techniques":["T1190"],"provenance":"ai"},{"stage":"primary","techniques":["T1059"],"provenance":"ai"}],"timeline":[{"date":"2021-01-26","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2021-3199","provenance":"source"},{"date":"2026-10-08","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://www.cisa.gov/news-events/cybersecurity-advisories/aa26-281a","provenance":"source"},{"date":"2026-10-08","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2026-10-08","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2021-26539","provenance":"source"}],"speed":{"daysToPublicExploit":null,"firstExploitFrom":null,"daysToKev":2081},"priority":{"score":79.5,"factors":[{"name":"In a KEV catalog","points":35.0,"detail":"listed in CISA KEV and VulnCheck KEV"},{"name":"Recent KEV listing","points":10.0,"detail":"added 21 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.64,"detail":"percentile 0.9822"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"2 NVD references tagged 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