CVE-2023-49786

Asterisk susceptible to Denial of Service via DTLS Hello packets during call initiation

MEDIUM
5.9
CVSS Score
Published: December 14, 2023 at 07:47 PM UTC
Updated: June 17, 2026 at 06:36 AM UTC
3 products affected across 3 vendorsAsteriskCertified AsteriskAsterisk

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Severity
MEDIUM5.9
Exploit prediction
EPSS 5%
SSVC
PoC

Description

Asterisk is an open source private branch exchange and telephony toolkit. In Asterisk prior to versions 18.20.1, 20.5.1, and 21.0.1; as well as certified-asterisk prior to 18.9-cert6; Asterisk is susceptible to a DoS due to a race condition in the hello handshake phase of the DTLS protocol when handling DTLS-SRTP for media setup. This attack can be done continuously, thus denying new DTLS-SRTP encrypted calls during the attack. Abuse of this vulnerability may lead to a massive Denial of Service on vulnerable Asterisk servers for calls that rely on DTLS-SRTP. Commit d7d7764cb07c8a1872804321302ef93bf62cba05 contains a fix, which is part of versions 18.20.1, 20.5.1, 21.0.1, amd 18.9-cert6.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 18.20.119.0.0 ≤ v < 20.5.121.0.0
Affected range stops below 18.20.1, so it looks safe — our inference, not a vendor statement
Affected range stops below 20.5.1, so it looks safe — our inference, not a vendor statement
v < 18.20.1v < 18.9-cert6v < 20.5.1= 21.0.0
Affected range stops below 18.20.1, so it looks safe — our inference, not a vendor statement
Affected range stops below 18.9-cert6, so it looks safe — our inference, not a vendor statement
Affected range stops below 20.5.1, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

SSVC — Action Prioritization

SSVCPoCAutomatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

Attack Vector
NETWORK
Complexity
HIGH
Privileges
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality
NONE
Integrity
NONE
Availability
HIGH
Vector?

Quick Info

StatusMODIFIED
CWE
CWE-703CWE-362

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