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.

Published: 2021-02-19 Last update: 2024-11-21 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-26713 is rated Low Risk (37.1/100): CVSS Medium severity, with low exploitation likelihood (EPSS 0.13%). Monitor for updates and reassess as exploit intelligence or EPSS changes.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2021-26713

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-30 0.16% 0.13% -0.04%
2 2025-11-21 0.12% 0.16% +0.04%
3 2025-11-18 — 0.12% —

Full EPSS history (10 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-26713

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L)
A normal user session is enough; they don’t have to be admin.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]
4.0 2.0 MEDIUM
AV:N/AC:L/Au:S/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:S)
A single authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 8.0 2.9 [email protected]

Weakness enumeration for CVE-2021-26713

OS Trackers for CVE-2021-26713

vendor priority summary link
alpine medium CVE-2021-26713: 1 source package rows (asterisk); 41 state rows across 10 repos (3.10-main, 3.11-main, 3.12-main, 3.17-main, 3.18-main, 3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 8, open 33. https://security.alpinelinux.org/vuln/CVE-2021-26713
debian unimportant CVE-2021-26713 unimportant priority: Debian including 1 source packages (asterisk), 2 status rows across 2 suites (bullseye, sid): resolved 2. https://security-tracker.debian.org/tracker/CVE-2021-26713
gentoo high CVE-2021-26713: 1 GLSA(s) (202412-03), 1 atom(s) (net-misc/asterisk); latest impact high. https://bugs.gentoo.org/buglist.cgi?quicksearch=CVE-2021-26713
ubuntu medium CVE-2021-26713 medium priority: Ubuntu including 1 source packages (asterisk), 16 status rows across 16 suites (bionic, focal, groovy, hirsute, impish, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): ignored 8, needed 3, not-affected 3, DNE 1, needs-triage 1. https://ubuntu.com/security/CVE-2021-26713

Affected software / configurations for CVE-2021-26713

Vendor Product Version Raw CPE
digium asterisk >= 16.0.0, < 16.16.1 cpe:2.3:a:digium:asterisk:*:*:*:*:*:*:*:*
digium asterisk >= 17.0.0, < 17.9.2 cpe:2.3:a:digium:asterisk:*:*:*:*:*:*:*:*
digium asterisk >= 18.0.0, < 18.2.1 cpe:2.3:a:digium:asterisk:*:*:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:-:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc1:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc2:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc3:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert1-rc4:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert2:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert3:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert4:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc1:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc2:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc3:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert4-rc4:*:*:*:*:*:*
digium certified_asterisk 16.8 cpe:2.3:a:digium:certified_asterisk:16.8:cert5:*:*:*:*:*:*

References for CVE-2021-26713

cvelogic Threat Intelligence