How severe is CVE-2021-26713?

CVE-2021-26713 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.

Is CVE-2021-26713 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-26713?

CVE-2021-26713 primarily affects Digium Asterisk. In total, 14 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-26713?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-26713 published?

CVE-2021-26713 was published on 2021-02-19 and last updated on 2026-06-17.

CVE-2021-26713

CVE-2021-26713 is a medium-severity vulnerability in Digium Asterisk with a CVSS 3.x base score of 6.5. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-787.

Key facts

Severity: Medium (CVSS 3.x base score 6.5)
CVSS v2: 4.0
EPSS exploit prediction: 2% (76th percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-787
Affected product: Digium Asterisk
Published: 2021-02-19
Last modified: 2026-06-17

Description

A stack-based buffer overflow in res_rtp_asterisk.c in Sangoma Asterisk before 16.16.1, 17.x before 17.9.2, and 18.x before 18.2.1 and Certified Asterisk before 16.8-cert6 allows an authenticated WebRTC client to cause an Asterisk crash by sending multiple hold/unhold requests in quick succession. This is caused by a signedness comparison mismatch.

Frequently asked questions

What is CVE-2021-26713?: A stack-based buffer overflow in res_rtp_asterisk.c in Sangoma Asterisk before 16.16.1, 17.x before 17.9.2, and 18.x before 18.2.1 and Certified Asterisk before 16.8-cert6 allows an authenticated WebRTC client to cause an Asterisk crash by sending multiple hold/unhold requests in quick succession. This is caused by a signedness comparison mismatch.
How severe is CVE-2021-26713?: CVE-2021-26713 has a CVSS 3.x base score of 6.5, rated medium severity. It is exploitable over network with low attack complexity, requires low privileges and no user interaction. Impact on confidentiality is none, integrity none, and availability high.
Is CVE-2021-26713 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 2% (76th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-26713?: CVE-2021-26713 primarily affects Digium Asterisk. In total, 14 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-26713?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-26713 published?: CVE-2021-26713 was published on 2021-02-19 and last updated on 2026-06-17.

References

Affected products (14)

cpe:2.3:a:digium:asterisk:*:*:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:-:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc1:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc2:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc3:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc4:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert2:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert3:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert4:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc1:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc2:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc3:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc4:*:*:*:*:*:*
cpe:2.3:a:digium:certified_asterisk:16.8:cert5:*:*:*:*:*:*

More vulnerabilities in Digium Asterisk

CVE-2022-26651 — Critical (CVSS 9.8): An issue was discovered in Asterisk through 19.x and Certified Asterisk through 16.8-cert13. The func_odbc module…
CVE-2017-14100 — Critical (CVSS 9.8): In Asterisk 11.x before 11.25.2, 13.x before 13.17.1, and 14.x before 14.6.1 and Certified Asterisk 11.x before…
CVE-2022-26499 — Critical (CVSS 9.1): An SSRF issue was discovered in Asterisk through 19.x. When using STIR/SHAKEN, it's possible to send arbitrary requests…
CVE-2014-8418 — Critical (CVSS 9.0): The DB dialplan function in Asterisk Open Source 1.8.x before 1.8.32, 11.x before 11.1.4.1, 12.x before 12.7.1, and…
CVE-2011-1599 — Critical (CVSS 9.0): manager.c in the Manager Interface in Asterisk Open Source 1.4.x before 1.4.40.1, 1.6.1.x before 1.6.1.25, 1.6.2.x…
CVE-2019-18610 — High (CVSS 8.8): An issue was discovered in manager.c in Sangoma Asterisk through 13.x, 16.x, 17.x and Certified Asterisk 13.21 through…

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