CVE-2023-49786 — Asterisk is an open source private branch exchange and telephony toolkit

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 DTL

01What is this vulnerability?

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…

02Affected products

Vendor	Product	Versions
asterisk	asterisk	< 18.20.1, >= 19.0.0, < 20.5.1, = 21.0.0, < 18.9-cert6

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2023-12-14T19:47:46.306Z
• Last modified: 2025-02-13T17:18:55.224Z

09References

• github.com — https://github.com/asterisk/asterisk/security/advisories/GHSA-hxj9-xwr8-w8pq
• github.com — https://github.com/asterisk/asterisk/commit/d7d7764cb07c8a1872804321302ef93bf62c…
• github.com — https://github.com/EnableSecurity/advisories/tree/master/ES2023-01-asterisk-dtls…
• www.openwall.com — http://www.openwall.com/lists/oss-security/2023/12/15/7
• packetstormsecurity.com — http://packetstormsecurity.com/files/176251/Asterisk-20.1.0-Denial-Of-Service.ht…
• seclists.org — http://seclists.org/fulldisclosure/2023/Dec/24
• lists.debian.org — https://lists.debian.org/debian-lts-announce/2023/12/msg00019.html