CVE-2021-46837

res_pjsip_t38 in Sangoma Asterisk 16.x before 16.16.2, 17.x before 17.9.3, and 18.x before 18.2.2, and Certified Asterisk before 16.8-cert7, allows an attacker to trigger a crash by sending an m=image line and zero port in a response to a T.38 re-invite initiated by Asterisk. This is a re-occurrence of the CVE-2019-15297 symptoms but not for exactly the same reason. The crash occurs because there is an append operation relative to the active topology, but this should instead be a replace operation.

Published: 2022-08-30 Last update: 2026-06-17 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2021-46837 is rated Moderate Risk (53.8/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.75%). EPSS rose +1.62% over the last day, indicating growing attacker interest. Review affected assets and schedule remediation.

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-2021-46837

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 2026-06-15 0.13% 1.75% +1.62%
2 2026-01-16 0.23% 0.13% -0.09%
3 2025-11-21 — 0.23% —

Full EPSS history (11 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2021-46837

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]

Weakness enumeration for CVE-2021-46837

OS Trackers for CVE-2021-46837

vendor priority summary link
alpine medium CVE-2021-46837: 1 source package rows (asterisk); 35 state rows across 5 repos (3.19-main, 3.20-main, 3.21-main, 3.22-main, edge-main); fixed 0, open 35. https://security.alpinelinux.org/vuln/CVE-2021-46837
debian not yet assigned CVE-2021-46837 not yet assigned priority: Debian including 1 source packages (asterisk), 2 status rows across 2 suites (bullseye, sid): resolved 2. https://security-tracker.debian.org/tracker/CVE-2021-46837
ubuntu medium CVE-2021-46837 medium priority: Ubuntu including 1 source packages (asterisk), 13 status rows across 13 suites (bionic, focal, jammy, kinetic, lunar, mantic, noble, oracular, plucky, questing, trusty, upstream, xenial): not-affected 8, needs-triage 3, ignored 1, released 1. https://ubuntu.com/security/CVE-2021-46837

Affected software / configurations for CVE-2021-46837

Vendor Product Version Raw CPE
asterisk certified_asterisk 16.8.0 cpe:2.3:a:asterisk:certified_asterisk:16.8.0:-:*:*:*:*:*:*
asterisk certified_asterisk 16.8.0 cpe:2.3:a:asterisk:certified_asterisk:16.8.0:cert1:*:*:*:*:*:*
asterisk certified_asterisk 16.8.0 cpe:2.3:a:asterisk:certified_asterisk:16.8.0:cert2:*:*:*:*:*:*
asterisk certified_asterisk 16.8.0 cpe:2.3:a:asterisk:certified_asterisk:16.8.0:cert3:*:*:*:*:*:*
asterisk certified_asterisk 16.8.0 cpe:2.3:a:asterisk:certified_asterisk:16.8.0:cert4:*:*:*:*:*:*
asterisk certified_asterisk 16.8.0 cpe:2.3:a:asterisk:certified_asterisk:16.8.0:cert5:*:*:*:*:*:*
asterisk certified_asterisk 16.8.0 cpe:2.3:a:asterisk:certified_asterisk:16.8.0:cert6:*:*:*:*:*:*
digium asterisk >= 16.0.0, < 16.16.2 cpe:2.3:a:digium:asterisk:*:*:*:*:*:*:*:*
digium asterisk >= 17.0.0, < 17.9.3 cpe:2.3:a:digium:asterisk:*:*:*:*:*:*:*:*
digium asterisk >= 18.0.0, < 18.2.2 cpe:2.3:a:digium:asterisk:*:*:*:*:*:*:*:*
debian debian_linux 9.0 cpe:2.3:o:debian:debian_linux:9.0:*:*:*:*:*:*:*
debian debian_linux 10.0 cpe:2.3:o:debian:debian_linux:10.0:*:*:*:*:*:*:*
debian debian_linux 11.0 cpe:2.3:o:debian:debian_linux:11.0:*:*:*:*:*:*:*

References for CVE-2021-46837

cvelogic Threat Intelligence