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Fencer Vulns
high 7.5

CVE-2023-49786 json

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

published 2023-12-14 2 y ago modified 2026-06-17 4 mo ago also EUVD-2023-53705

cvss
7.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
5.3%
EPSS 5.3% chance of exploitation in 30 days, percentile 92%
public exploits
0
none known

Summary

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.

Patch / fix

  • digium asterisk 18.20.1, 20.5.1
  • asterisk Debian 14 1:20.5.1~dfsg+~cs6.13.40431414-1

debian advisories DEBIAN-CVE-2023-49786

  • asterisk Alpine 3.18, Alpine 3.17, Alpine 3.16 18.20.2-r0
  • asterisk Alpine 3.24, Alpine 3.23, Alpine 3.22 +3 more 20.5.1-r0

alpine advisories ALPINE-CVE-2023-49786

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2023-49786 updated cvss 7.5

asterisk: race condition in the hello handshake phase of the DTLS protocol triggers denial of service

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
yes
Technical impact
partial
Assessed
2 y ago

Exploit prediction

5.29% chance of exploitation in the next 30 days, higher than 92% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/asterisk/asterisk/security/advisories/GHSA-hxj9-xwr8-w8pq referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/EnableSecurity/advisories/tree/master/ES2023-01-asterisk-dtls-hello-race referenced PoC, tagged "exploit" by a source, unverified
  • openwall.com http://www.openwall.com/lists/oss-security/2023/12/15/7 referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com http://packetstormsecurity.com/files/176251/Asterisk-20.1.0-Denial-Of-Service.html referenced PoC, tagged "exploit" by a source, unverified
  • seclists.org http://seclists.org/fulldisclosure/2023/Dec/24 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
NVD 3.1 5.9 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected products

  • asterisk asterisk

Classification

Weakness
  • CWE-703 Improper Check or Handling of Exceptional Conditions
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.