{"id":"CVE-2020-35730","published":"2020-12-28T20:15:13Z","modified":"2026-06-17T03:14:12Z","title":"Roundcube Webmail Cross-Site Scripting (XSS) Vulnerability","vendor":"Roundcube","product":"Roundcube Webmail","tier":"core","eol":null,"description":{"text":"An XSS issue was discovered in Roundcube Webmail before 1.2.13, 1.3.x before 1.3.16, and 1.4.x before 1.4.10. The attacker can send a plain text e-mail message, with JavaScript in a link reference element that is mishandled by linkref_addindex in rcube_string_replacer.php.","provenance":"source","from":"NVD"},"summary":{"text":"A cross-site scripting flaw in Roundcube Webmail's handling of link reference elements, in the linkref_addindex function of rcube_string_replacer.php, affects versions before 1.2.13, 1.3.x before 1.3.16, and 1.4.x before 1.4.10. An attacker can send a plain text e-mail containing JavaScript in a link reference, which executes in the victim's browser when they interact with the message, requiring no authentication but user interaction.","provenance":"ai","model":"claude-haiku-5-5","generatedAt":"2026-10-31T05:10:44Z"},"cvss":{"score":6.1,"severity":"MEDIUM","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N","provenance":"source","from":"NVD"},"epss":{"score":0.3292,"percentile":0.98354,"date":"2026-10-30","provenance":"source"},"kev":{"dateAdded":"2023-06-22","dueDate":"2023-07-13","ransomware":false,"requiredAction":"Apply updates per vendor instructions.","notes":"https://roundcube.net/news/2020/12/27/security-updates-1.4.10-1.3.16-and-1.2.13; https://nvd.nist.gov/vuln/detail/CVE-2020-35730","provenance":"source"},"vulncheckKev":{"dateAdded":"2023-06-20","exploitedFirstSeen":"2023-06-20","ransomware":false,"evidence":[{"url":"https://cert.gov.ua/article/4905829","date":"2023-06-20"},{"url":"https://go.recordedfuture.com/hubfs/reports/cta-2023-0620.pdf","date":"2023-06-20"},{"url":"https://www.recordedfuture.com/bluedelta-exploits-ukrainian-government-roundcube-mail-servers","date":"2023-06-20"},{"url":"https://www.cisa.gov/sites/default/files/feeds/known_exploited_vulnerabilities.json","date":"2023-06-22"},{"url":"https://blog.eclecticiq.com/spearphishing-campaign-targets-zimbra-webmail-portals-of-government-organizations","date":"2023-07-17"},{"url":"https://www.welivesecurity.com/en/eset-research/winter-vivern-exploits-zero-day-vulnerability-roundcube-webmail-servers/","date":"2023-10-25"},{"url":"https://redalert.nshc.net/blog/","date":"2024-05-29"},{"url":"https://labs.withsecure.com/publications/mass-exploitation-the-vulnerable-edge-of-enterprise-security","date":"2024-06-12"},{"url":"https://redalert.nshc.net/2024/07/29/2023-activities-summary-of-sectorc-groups-jpn/","date":"2024-07-29"},{"url":"https://www.maverits.com/post/apt28-the-long-hand-of-russian-interests","date":"2025-01-25"}],"evidenceTotal":16,"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-79","name":"Improper Neutralization of Input During Web Page Generation"}],"references":[{"url":"https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=978491","tags":["Issue Tracking","Mailing List"]},{"url":"https://github.com/roundcube/roundcubemail/compare/1.4.9...1.4.10","tags":["Patch"]},{"url":"https://github.com/roundcube/roundcubemail/releases/tag/1.2.13","tags":["Release Notes"]},{"url":"https://github.com/roundcube/roundcubemail/releases/tag/1.3.16","tags":["Release Notes"]},{"url":"https://github.com/roundcube/roundcubemail/releases/tag/1.4.10","tags":["Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HCEU4BM5WGIDJWP6Z4PCH62ZMH57QYM2/","tags":["Mailing List","Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HMLIZWKMTRCLU7KZLEQHELS4INXJ7X5Q/","tags":["Mailing List","Release Notes"]},{"url":"https://roundcube.net/download/","tags":["Product"]},{"url":"https://www.alexbirnberg.com/roundcube-xss.html","tags":["Broken Link"]},{"url":"https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=978491","tags":["Issue Tracking","Mailing List"]},{"url":"https://github.com/roundcube/roundcubemail/compare/1.4.9...1.4.10","tags":["Patch"]},{"url":"https://github.com/roundcube/roundcubemail/releases/tag/1.2.13","tags":["Release Notes"]},{"url":"https://github.com/roundcube/roundcubemail/releases/tag/1.3.16","tags":["Release Notes"]},{"url":"https://github.com/roundcube/roundcubemail/releases/tag/1.4.10","tags":["Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HCEU4BM5WGIDJWP6Z4PCH62ZMH57QYM2/","tags":["Mailing List","Release Notes"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/HMLIZWKMTRCLU7KZLEQHELS4INXJ7X5Q/","tags":["Mailing List","Release Notes"]},{"url":"https://roundcube.net/download/","tags":["Product"]},{"url":"https://www.alexbirnberg.com/roundcube-xss.html","tags":["Broken Link"]},{"url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-35730","tags":["US Government Resource"]}],"techniques":[{"id":"T1189","name":"Drive-by Compromise","tactics":["initial-access"],"provenance":"ai","basis":"ai-mapping","bases":["ai-mapping"],"basisDetail":"claude-haiku-5-5: Malicious email content delivered to victim's browser","mappingType":"exploitation_technique","evidence":[{"from":"description","quote":"The attacker can send a plain text e-mail message","start":110,"end":159}],"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: JavaScript executes in victim's browser context","mappingType":"primary_impact","evidence":[{"from":"description","quote":"JavaScript in a link reference element","start":166,"end":204}],"model":"claude-haiku-5-5","confidence":"medium","confidenceNote":"AI-mapped from the description (quote-validated, not expert-reviewed)"}],"reports":[],"affected":[],"advisories":[],"euvd":{"id":"EUVD-2020-23386","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2020-23386","exploited":true,"exploitedSince":"2023-06-22","provenance":"source"},"exploits":[],"exploitSources":{"pocGithub":{"count":1,"skipped":0,"earliest":"2025-04-20","earliestUrl":"https://github.com/skyllpro/CVE-2021-44026-PoC","repos":[{"name":"skyllpro/CVE-2021-44026-PoC","url":"https://github.com/skyllpro/CVE-2021-44026-PoC","stars":0,"created":"2025-04-20"}]},"first":{"date":"2025-04-20","source":"PoC-in-GitHub","url":"https://github.com/skyllpro/CVE-2021-44026-PoC"},"provenance":"source"},"exploitRefs":[],"flow":[{"stage":"exploitation","techniques":["T1189"],"provenance":"ai"},{"stage":"primary","techniques":["T1059"],"provenance":"ai"}],"timeline":[{"date":"2020-12-28","kind":"published","label":"Published (NVD)","url":"https://nvd.nist.gov/vuln/detail/CVE-2020-35730","provenance":"source"},{"date":"2023-06-20","kind":"exploited-reported","label":"Exploitation first reported (VulnCheck KEV evidence)","url":"https://cert.gov.ua/article/4905829","provenance":"source"},{"date":"2023-06-22","kind":"kev","label":"Added to CISA KEV","url":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","provenance":"source"},{"date":"2023-06-22","kind":"euvd-exploited","label":"ENISA EUVD: exploited","url":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2020-23386","provenance":"source"},{"date":"2025-04-20","kind":"exploit-public","label":"First public exploit: PoC-in-GitHub","url":"https://github.com/skyllpro/CVE-2021-44026-PoC","provenance":"source"}],"speed":{"daysToPublicExploit":1574,"firstExploitFrom":"PoC-in-GitHub","daysToKev":906},"priority":{"score":66.9,"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 1229 days ago"},{"name":"Known ransomware use","points":0.0,"detail":"not known"},{"name":"EPSS percentile","points":19.67,"detail":"percentile 0.9835"},{"name":"Named in threat reports","points":0.0,"detail":"0 reports"},{"name":"Public exploit code","points":5.0,"detail":"1 PoC-in-GitHub repo"},{"name":"Mentioned in OTX pulses","points":3.0,"detail":"50 pulses"},{"name":"CVSS severity","points":4.27,"detail":"base score 6.1"},{"name":"End-of-life product","points":0.0,"detail":"supported or unknown"}]},"lineage":{"familyId":"fam-class-roundcube-webmail-cwe-79"}}