CVE-2021-26717
An issue was discovered in Sangoma Asterisk 16.x before 16.16.1, 17.x before 17.9.2, and 18.x...
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.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
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.
- Record
CVE-2021-26717- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - CVSS 2.0
- 5.0 Medium
AV:N/AC:L/Au:N/C:N/I:N/A:P - Updated
- 2026-11-02
CVE List No score
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.
- Record
CVE-2021-26717- Updated
- 2026-11-02
EUVDEUVD-2021-13505 No score
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.
- Record
EUVD-2021-13505- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-9mrj-wq9r-h4vw No score
An issue was discovered in Sangoma Asterisk 16.x before 16.16.1, 17.x before 17.9.2, and 18.x...
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.
- Record
GHSA-9mrj-wq9r-h4vw- Updated
- 2026-11-02
OSVALPINE-CVE-2021-26717
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.
- Record
ALPINE-CVE-2021-26717- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSV
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.
- Record
CVE-2021-26717- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVDEBIAN-CVE-2021-26717
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.
- Record
DEBIAN-CVE-2021-26717- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2021-26717
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.
- Record
UBUNTU-CVE-2021-26717- CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
asteriskAlpine:v3.12 |
16.0.0 up to 16.16.1-r0 | 16.16.1-r0 |
asteriskAlpine:v3.13 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
asteriskAlpine:v3.14 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
asteriskAlpine:v3.15 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
asteriskAlpine:v3.16 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
asteriskAlpine:v3.17 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
asteriskAlpine:v3.18 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
asteriskAlpine:v3.19 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
asteriskAlpine:v3.20 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
asteriskAlpine:v3.21 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
Show 9 moreShow less
| Package | Affected | Fixed |
|---|---|---|
asteriskAlpine:v3.22 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
asteriskAlpine:v3.23 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
asteriskAlpine:v3.24 |
16.0.0 up to 18.2.1-r0 | 18.2.1-r0 |
asteriskDebian:14 |
before 1:16.16.1~dfsg-1, plus listed versions 0.1.11-30.1.11-3woody11:1.0.5-21:1.0.5-41:1.0.6-1 Show 45 moreShow less1:1.0.6-21:1.0.7-11:1.0.7.dfsg.1-11:1.0.7.dfsg.1-21:1.0.7.dfsg.1-2sarge11:1.0.7.dfsg.1-2sarge21:1.0.7.dfsg.1-2sarge31:1.0.7.dfsg.1-2sarge41:1.0.7.dfsg.1-2sarge51:1.0.7.dfsg.1-2sarge61:1.0.9.dfsg-11:1.0.9.dfsg-31:1.0.9.dfsg-41:1.0.9.dfsg-51:1.0.9.dfsg-61:1.2.0-beta1.dfsg-11:1.2.0-beta2.dfsg-11:1.2.0-beta2.dfsg-21:1.2.0-beta2.dfsg-31:1.2.0-rc1.dfsg-11:1.2.0-rc2.dfsg-11:1.2.0.dfsg-11:1.2.0.dfsg-21:1.2.0.dfsg-31:1.2.0.dfsg-41:1.2.0.dfsg-51:1.2.0.dfsg-61:1.2.1.dfsg-11:1.2.1.dfsg-21:1.2.1.dfsg-31:1.2.10.dfsg-11:1.2.10.dfsg-1bpo11:1.2.10.dfsg-21:1.2.10.dfsg-31:1.2.11.dfsg-11:1.2.12.1.dfsg-11:1.2.13~dfsg-11:1.2.13~dfsg-21:1.2.13~dfsg-2etch11:1.2.13~dfsg-2etch21:1.2.13~dfsg-2etch31:1.2.13~dfsg-2etch41:1.2.14~dfsg-11:1.2.14~dfsg-21:1.2.14~dfsg-3 |
1:16.16.1~dfsg-1 |
asteriskUbuntu:22.04:LTS |
All versions, plus listed versions 1:16.16.1~dfsg-21:16.16.1~dfsg-41:16.16.1~dfsg-4build11:16.16.1~dfsg+~2.10-11:18.10.0~dfsg+~cs6.10.40431411-2 |
None known |
asteriskUbuntu:24.04:LTS |
All versions, plus listed versions 1:20.4.0~dfsg+~cs6.13.40431414-21:20.5.0~dfsg+~cs6.13.40431414-11:20.5.1~dfsg+~cs6.13.40431414-11:20.5.2~dfsg+~cs6.13.40431414-11:20.6.0~dfsg+~cs6.13.40431414-1 Show 4 moreShow less1:20.6.0~dfsg+~cs6.13.40431414-21:20.6.0~dfsg+~cs6.13.40431414-2build31:20.6.0~dfsg+~cs6.13.40431414-2build41:20.6.0~dfsg+~cs6.13.40431414-2build5 |
None known |
asteriskUbuntu:25.10 |
All versions, plus listed versions 1:22.2.0~dfsg+~cs6.15.60671435-21:22.3.0~dfsg+~cs6.15.60671435-11:22.4.1~dfsg+~cs6.15.60671435-11:22.4.1~dfsg+~cs6.15.60671435-21:22.5.1~dfsg+~cs6.15.60671435-11:22.5.2~dfsg+~cs6.15.60671435-1 |
None known |
asteriskUbuntu:26.10 |
All versions, plus listed versions 1:22.5.2~dfsg+~cs6.15.60671435-11:22.10.0+dfsg+~cs6.17.60671434-1ubuntu21:22.10.0+dfsg+~cs6.17.60671434-1ubuntu3 |
None known |
asteriskUbuntu:26.04:LTS |
All versions, plus listed versions 1:22.5.2~dfsg+~cs6.15.60671435-1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| aliases | EUVD | |
| first indexed | CVE List, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2021-26717 is a high vulnerability (CVSS 7.5) in Digium Asterisk, published February 18, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 2.20%, the 82nd percentile. Fixed in asterisk 16.16.1-r0.
References
downloads.asterisk.org/pub/security
seclists.org/fulldisclosure/2021/Feb/58
issues.asterisk.org/jira/browse/ASTERISK-29203
packetstormsecurity.com/files/161471/Asterisk-Project-Security-Advisory-AST-2021-002.html
nvd.nist.gov/vuln/detail/CVE-2021-26717
Left out here: 187 versions. The JSON record has them.