{"id":"CVE-2021-26717","url":"https://www.cyber-defence.io/tools/cve/CVE-2021-26717","generatedAt":"2026-10-27T22:33:57.549Z","title":"When re-negotiating for T.38, if the initial remote response was delayed just enough, Asterisk would send both audio and T.38 in the SDP.","description":"An issue was discovered in Sangoma Asterisk 16.x before 16.16.1, 17.x before 17.9.2, and 18.x before 18.2.1 and Certified Asterisk before 16.8-cert6. When re-negotiating for T.38, if the initial remote response was delayed just enough, Asterisk would send both audio and T.38 in the SDP. If this happened, and the remote responded with a declined T.38 stream, then Asterisk would crash.","published":"2021-02-18T20:15:13.000Z","lastModified":"2026-06-17T03:43:43.000Z","status":"Modified","sourceIdentifier":"cve@mitre.org","cvss":{"version":"3.1","score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"},"cwe":[],"affected":["digium/asterisk","digium/certified asterisk"],"epss":{"score":0.02204,"percentile":0.82428,"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":"high","text":"High impact if exploited, but EPSS currently rates exploitation as unlikely (2.20%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit."},"changes":[],"references":[{"url":"http://packetstormsecurity.com/files/161471/Asterisk-Project-Security-Advisory-AST-2021-002.html","tags":["Third Party Advisory"],"source":"cve@mitre.org"},{"url":"http://seclists.org/fulldisclosure/2021/Feb/58","tags":["Mailing List","Patch","Third Party Advisory"],"source":"cve@mitre.org"},{"url":"https://downloads.asterisk.org/pub/security/","tags":["Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://downloads.asterisk.org/pub/security/AST-2021-002.html","tags":["Vendor Advisory"],"source":"cve@mitre.org"},{"url":"https://issues.asterisk.org/jira/browse/ASTERISK-29203","tags":["Issue Tracking","Patch","Vendor Advisory"],"source":"cve@mitre.org"},{"url":"http://packetstormsecurity.com/files/161471/Asterisk-Project-Security-Advisory-AST-2021-002.html","tags":["Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"http://seclists.org/fulldisclosure/2021/Feb/58","tags":["Mailing List","Patch","Third Party Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://downloads.asterisk.org/pub/security/","tags":["Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://downloads.asterisk.org/pub/security/AST-2021-002.html","tags":["Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"},{"url":"https://issues.asterisk.org/jira/browse/ASTERISK-29203","tags":["Issue Tracking","Patch","Vendor Advisory"],"source":"af854a3a-2127-422b-91ae-364da2661108"}],"sources":{"nvd":"https://nvd.nist.gov/vuln/detail/CVE-2021-26717","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."}