High
Security advisory
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.
- Products
- Not specified
- Affected versions
- Not specified
- Fixed versions
- Not specified
- CVEs
- CVE-2021-26717
- Confirmed fixed CVEs
- Not specified
- Updated in this feed
- 1 Nov 2026, 05:21 UTC · Revision 1
Source evidence
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.
osv:CVE-2021-26717
Complete source record
{
"id": "8232e1966ceab4cf40b7a95a622df56e59aa93043928d153aedaa3f83a9f9f9f",
"url": "https://osv.dev/vulnerability/CVE-2021-26717",
"method": "structured",
"payload": {
"kind": "advisory",
"title": "CVE-2021-26717",
"summary": "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.",
"evidence": "osv:CVE-2021-26717",
"products": [],
"severity": "high",
"structured": {
"id": "CVE-2021-26717",
"aliases": [
"CVE-2021-26717"
],
"metrics": [
{
"type": "CVSS_V3",
"score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H"
}
],
"affected": [
{
"ranges": [
{
"repo": "https://github.com/asterisk/asterisk",
"type": "GIT",
"events": [
{
"introduced": "a65908f83e2f17a3aca7eb39c8e06045aca02674"
},
{
"fixed": "3cd8afbdf2c6dffe80c631a5336e21bb1827a5cd"
},
{
"introduced": "5ffe12b6ef30cd503f85d75745fd8d9c2cfafe47"
},
{
"fixed": "fdaf2d0689b7a8928a45019c9af14c53bcdfa6e3"
},
{
"introduced": "2c1bba3cbec008c8ce35c78a2c79f9f207ea58bc"
},
{
"fixed": "332130c4389803a3c7e63cabf00daf5ac66a3068"
},
{
"introduced": "d436f568583184a13aa46349af5a3f0907087b44"
},
{
"last_affected": "10b274d1aba4fc2cf2a8cabcb66eb2a049e2250f"
}
],
"database_specific": {
"extracted_events": [
{
"cpe": "cpe:2.3:a:digium:asterisk:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "16.0.0"
},
{
"fixed": "16.16.1"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:digium:asterisk:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "17.0.0"
},
{
"fixed": "17.9.2"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:digium:asterisk:*:*:*:*:*:*:*:*",
"range": [
{
"introduced": "18.0"
},
{
"fixed": "18.2.1"
}
],
"source": "CPE_RANGE"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:-:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-NA"
},
{
"last_affected": "16.8-NA"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc1:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert1\\-rc1"
},
{
"last_affected": "16.8-cert1\\-rc1"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc2:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert1\\-rc2"
},
{
"last_affected": "16.8-cert1\\-rc2"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc3:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert1\\-rc3"
},
{
"last_affected": "16.8-cert1\\-rc3"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc4:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert1\\-rc4"
},
{
"last_affected": "16.8-cert1\\-rc4"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert2:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert2"
},
{
"last_affected": "16.8-cert2"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert3:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert3"
},
{
"last_affected": "16.8-cert3"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert4:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert4"
},
{
"last_affected": "16.8-cert4"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc1:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert4\\-rc1"
},
{
"last_affected": "16.8-cert4\\-rc1"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc2:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert4\\-rc2"
},
{
"last_affected": "16.8-cert4\\-rc2"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc3:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert4\\-rc3"
},
{
"last_affected": "16.8-cert4\\-rc3"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc4:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert4\\-rc4"
},
{
"last_affected": "16.8-cert4\\-rc4"
}
],
"source": "CPE_STRING"
},
{
"cpe": "cpe:2.3:a:digium:certified_asterisk:16.8:cert5:*:*:*:*:*:*",
"range": [
{
"introduced": "16.8-cert5"
},
{
"last_affected": "16.8-cert5"
}
],
"source": "CPE_STRING"
}
]
}
}
],
"versions": [
"16.8-NA",
"16.8-cert1\\-rc1",
"16.8-cert1\\-rc2",
"16.8-cert1\\-rc3",
"16.8-cert1\\-rc4",
"16.8-cert2",
"16.8-cert3",
"16.8-cert4",
"16.8-cert4\\-rc1",
"16.8-cert4\\-rc2",
"16.8-cert4\\-rc3",
"16.8-cert4\\-rc4",
"16.8-cert5",
"certified/16.8-cert5",
"certified/16.8-cert4",
"certified/16.8-cert4-rc4",
"certified/16.8-cert4-rc3",
"certified/16.8-cert4-rc2",
"certified/16.8-cert4-rc1",
"certified/16.8-cert3",
"certified/16.8-cert2",
"certified/16.8-cert1",
"certified/16.8-cert1-rc5",
"certified/16.8-cert1-rc4",
"certified/16.8-cert1-rc3",
"certified/16.8-cert1-rc2",
"certified/16.8-cert1-rc1",
"16.8.0"
],
"database_specific": {
"source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2021-26717.json"
}
}
],
"modified": "2026-10-24T10:30:27.563051804Z",
"provider": "osv",
"references": [
"https://downloads.asterisk.org/pub/security/",
"https://downloads.asterisk.org/pub/security/AST-2021-002.html",
"https://issues.asterisk.org/jira/browse/ASTERISK-29203"
],
"provider_metadata": {}
},
"related_cves": [
{
"value": "CVE-2021-26717",
"evidence": "/id"
}
],
"security_relevant": true,
"severity_evidence": "/severity/0/score"
},
"source_id": "core-osv",
"document_id": 431857,
"published_at": "2021-02-18T20:15:12.667+00:00"
}