# CVE-2023-49786: Asterisk susceptible to Denial of Service via DTLS Hello packets during call initiation

> Attackers can cause a Denial of Service on Asterisk servers by exploiting a race condition in DTLS-SRTP handshakes, blocking new encrypted calls.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 14 Dec 2023
- **Updated:** 13 Feb 2025
- **Also known as:** ALPINE-CVE-2023-49786, DEBIAN-CVE-2023-49786, GHSA-hxj9-xwr8-w8pq, UBUNTU-CVE-2023-49786

## What is CVE-2023-49786?

CVE-2023-49786 is a high-severity vulnerability in Digium Asterisk, published on 14 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official 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.

Weakness: CWE-362 (Concurrent Execution using Shared Resource with Improper Synchronization), CWE-703 (Improper Check or Handling of Exceptional Conditions)

## Which versions are affected by CVE-2023-49786?

It affects 2 products.


Products: Digium Asterisk, Sangoma Certified Asterisk.

## How do I fix CVE-2023-49786?

Upgrade to a fixed version.

## Is CVE-2023-49786 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-49786 exists.

## Other vulnerabilities in Digium Asterisk

- [CVE-2017-14100](https://insights.sbomify.com/CVE-2017-14100/): Command injection in n/a (critical 9.8)
- [CVE-2014-8418](https://insights.sbomify.com/CVE-2014-8418/): Privilege escalation in n/a (critical 9.0)
- [CVE-2011-1599](https://insights.sbomify.com/CVE-2011-1599/): Missing authorization in n/a (critical 9.0)
- [CVE-2017-16671](https://insights.sbomify.com/CVE-2017-16671/): Memory corruption in n/a (high 8.8)
- [CVE-2017-7617](https://insights.sbomify.com/CVE-2017-7617/): Memory corruption in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-49786 and fix it if it is affected.

What it is: CVE-2023-49786 is a high-severity vulnerability in Digium Asterisk, published on 14 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-49786 exists.

Affected product: Digium Asterisk. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2023-49786/ (Markdown: https://insights.sbomify.com/CVE-2023-49786/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-49786
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-49786
- OSV: https://osv.dev/vulnerability/CVE-2023-49786

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From sbomify Insights: https://insights.sbomify.com/CVE-2023-49786/
Summaries are generated and may contain mistakes; the official description above is the record.