{"id":"CVE-2026-66911","kind":"vulnerability","aliases":["CVE-2026-66911"],"related":[],"title":"Zimbra: crafted email attachment runs JavaScript in webmail","description":"Zimbra is vulnerable to stored cross-site scripting (XSS) via the Content-Location MIME header in email attachments. Due to lack of sanitization of the Content-Location header, an attacker can set it to a javascript: URI. An unauthenticated remote attacker can send a crafted email to a victim; when the victim opens the email in the Zimbra web interface and clicks the attachment name, the JavaScript payload executes in the victim's browser context. This issue was fixed in version 10.1.21","summary":"Zimbra does not sanitize the Content-Location header on email attachments, so a javascript: URI can be stored there. When a victim opens the crafted email and clicks the attachment name, the script runs in their browser inside Zimbra.","severity":"medium","cvss":5.3,"epss":null,"exploited":false,"exploited_at":null,"products":[],"ecosystems":[],"tags":["other","self-hosted","webmail","zimbra"],"not_affected_if":["version-at-or-above-10.1.21"],"how_to_check":"- Check the installed Zimbra version against the fixed version stated in the sources, `10.1.21`.","fix":"- Zimbra: `10.1.21` or later\n- Sources do not state fixes for other release lines.","status":"open","published_at":"2026-10-29T16:18:15+00:00","first_seen_at":"2026-10-29T16:26:01+00:00","triaged_at":"2026-10-29T16:31:49+00:00","updated_at":"2026-10-29T16:31:49+00:00","category":"other","confidence":0.7,"triage":{"at":"2026-10-29T16:31:49Z","model":"claude-haiku-5-5","output":{"fix":"- Zimbra: `10.1.21` or later\n- Sources do not state fixes for other release lines.","reach":"internet","title":"Zimbra: crafted email attachment runs JavaScript in webmail","impact":"medium","summary":"Zimbra does not sanitize the Content-Location header on email attachments, so a javascript: URI can be stored there. When a victim opens the crafted email and clicks the attachment name, the script runs in their browser inside Zimbra.","audience":"businesses","category":"other","nicknames":[],"who_cares":["zimbra","webmail","self-hosted"],"confidence":0.7,"fix_status":"available","needs_auth":"no","worst_case":"Script runs in the victim's browser session inside Zimbra","analyst_note":"","how_to_check":"- Check the installed Zimbra version against the fixed version stated in the sources, `10.1.21`.\n- unknown","plain_action":"","needs_analyst":false,"not_affected_if":["version-at-or-above-10.1.21"],"who_is_affected":"Any Zimbra web interface deployment that displays email attachments can be exposed, since a victim only needs to open the crafted email and click the attachment name. Sources do not say which Zimbra release lines are affected beyond the fix in 10.1.21, and they do not describe any non-default configuration required.","user_interaction":"yes","needs_special_setup":"unknown","severity_if_unknown":"medium"},"cost_usd":0.000668,"input_tokens":4194,"output_tokens":497,"severity_before":"medium"},"analyst_status":null,"analyst_note":null,"search":"'-2026':10A,13A '-66911':11A,14A '10.1.21':145C 'attach':4A,32B,51B,80C,127C 'attack':93C,104C 'browser':58B,137C 'click':49B,125C 'content':27B,74C,89C 'content-loc':26B,73C,88C 'context':138C 'craft':2A,46B,108C 'cross':67C 'cross-sit':66C 'cve':9A,12A 'due':81C 'email':3A,31B,47B,79C,109C,118C 'execut':132C 'fix':142C 'header':29B,77C,91C 'host':18B 'insid':59B 'interfac':123C 'issu':140C 'javascript':6A,35B,99C,130C 'lack':83C 'locat':28B,75C,90C 'mime':76C 'name':52B,128C 'open':44B,116C 'payload':131C 'remot':103C 'run':5A,55B 'sanit':24B,85C 'script':54B,69C 'self':17B 'self-host':16B 'send':106C 'set':95C 'site':68C 'store':39B,65C 'unauthent':102C 'uri':36B,100C 'version':144C 'via':71C 'victim':43B,112C,115C,135C 'vulner':63C 'web':122C 'webmail':8A,19B 'xss':70C 'zimbra':1A,20B,21B,60B,61C,121C","nicknames":[],"mitigations":[],"who_affected":"Any Zimbra web interface deployment that displays email attachments can be exposed, since a victim only needs to open the crafted email and click the attachment name. Sources do not say which Zimbra release lines are affected beyond the fix in 10.1.21, and they do not describe any non-default configuration required.","tier":"C","verified":{},"analyst_revisit_at":null,"fix_status":"available","audience":"businesses","plain_action":null,"first_public_at":"2026-10-29T16:18:15+00:00","kev":null,"cvss_vector":"CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X","cvss_by":"cvd@cert.pl","poc_count":0,"sources":[{"source":"nvd","external_id":"CVE-2026-66911","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-66911","severity":null,"published_at":"2026-10-29T16:18:15+00:00","modified_at":"2026-10-29T16:18:15+00:00","first_seen_at":"2026-10-29T16:26:01+00:00","fetched_at":"2026-10-29T16:26:01+00:00","note":null}],"documents":[],"notice":"Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai"}