{"id":"CVE-2021-30477","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-30477","generatedAt":"2026-10-27T21:19:37.625Z","title":"An issue was discovered in Zulip Server before 3.4.","description":"An issue was discovered in Zulip Server before 3.4. A bug in the implementation of replies to messages sent by outgoing webhooks to private streams meant that an outgoing webhook bot could be used to send messages to private streams that the user was not intended to be able to send messages to.","published":"2021-04-15T00:15:13.000Z","lastModified":"2026-06-17T03:50:19.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":4.3,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:L/A:N"},"cwe":[],"affected":["zulip/zulip server"],"epss":{"score":0.00656,"percentile":0.51125,"date":"2026-10-26","history":[]},"kev":{"listed":false},"exploits":{"count":0,"verified":false,"firstPublished":null,"source":"Exploit-DB (https://gitlab.com/exploit-database/exploitdb)","entries":[]},"verdict":{"level":"low","text":"Lower severity and a low EPSS score (0.66%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://blog.zulip.com/2021/04/14/zulip-server-3-4/","tags":["Release Notes","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://blog.zulip.com/2021/04/14/zulip-server-3-4/","tags":["Release Notes","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-30477","epss":"https://www.first.org/epss/","kev":"https://www.cisa.gov/known-exploited-vulnerabilities-catalog","exploitdb":"https://www.exploit-db.com/"},"licence":"CC BY 4.0 — link back to the CVE Explorer if you publish the results; upstream data remains subject to its own terms."}