{"id":"CVE-2021-0205","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-0205","generatedAt":"2026-10-27T23:27:31.793Z","title":"When the \"Intrusion Detection Service\" (IDS) feature is configured on Juniper Networks MX series with a dynamic firewall filter using IPv6 source or destination prefix, it may incorrectly match the prefix as /32, causing the filter to block unexpected…","description":"When the \"Intrusion Detection Service\" (IDS) feature is configured on Juniper Networks MX series with a dynamic firewall filter using IPv6 source or destination prefix, it may incorrectly match the prefix as /32, causing the filter to block unexpected traffic. This issue affects only IPv6 prefixes when used as source and destination. This issue affects MX Series devices using MS-MPC, MS-MIC or MS-SPC3 service cards with IDS service configured. This issue affects: Juniper Networks Junos OS 17.3 versions prior to 17.3R3-S10 on MX Series; 17.4 versions prior to 17.4R3-S3 on MX Series; 18.1 versions prior to 18.1R3-S11 on MX Series; 18.2 versions prior to 18.2R3-S6 on MX Series; 18.3 versions prior to 18.3R3-S4 on MX Series; 18.4 versions prior to 18.4R3-S6 on MX Series; 19.1 versions prior to 19.1R2-S2, 19.1R3-S3 on MX Series; 19.2 versions prior to 19.2R3-S1 on MX Series; 19.3 versions prior to 19.3R2-S5, 19.3R3-S1 on MX Series; 19.4 versions prior to 19.4R3 on MX Series; 20.1 versions prior to 20.1R2 on MX Series; 20.2 versions prior to 20.2R2 on MX Series;","published":"2021-01-15T18:15:15.000Z","lastModified":"2026-06-17T03:29:29.000Z","status":"Modified","sourceIdentifier":"sirt@juniper.net","cvss":{"version":"3.1","score":5.8,"severity":"MEDIUM","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L"},"cwe":["CWE-284"],"affected":["juniper/junos"],"epss":{"score":0.01217,"percentile":0.68399,"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 (1.22%). Track it; it rarely justifies an emergency change on its own."},"changes":[],"references":[{"url":"https://kb.juniper.net/JSA11095","tags":["Vendor Advisory"],"source":"sirt@juniper.net"},{"url":"https://kb.juniper.net/JSA11095","tags":["Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-0205","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."}