# CVE-2023-51443: FreeSWITCH susceptible to Denial of Service via DTLS Hello packets during call initiation

> Attackers can cause denial of service on FreeSWITCH servers by exploiting a race condition in DTLS-SRTP handshake handling during call initiation.

- **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:** 27 Dec 2023
- **Updated:** 4 Nov 2025
- **Also known as:** ALPINE-CVE-2023-51443, GHSA-39gv-hq72-j6m6

## What is CVE-2023-51443?

CVE-2023-51443 is a high-severity vulnerability in signalwire freeswitch, published on 27 Dec 2023. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

FreeSWITCH is a Software Defined Telecom Stack enabling the digital transformation from proprietary telecom switches to a software implementation that runs on any commodity hardware. Prior to version 1.10.11, when handling DTLS-SRTP for media setup, FreeSWITCH is susceptible to Denial of Service due to a race condition in the hello handshake phase of the DTLS protocol. This attack can be done continuously, thus denying new DTLS-SRTP encrypted calls during the attack. If an attacker manages to send a ClientHello DTLS message with an invalid CipherSuite (such as `TLS_NULL_WITH_NULL_NULL`) to the port on the FreeSWITCH server that is expecting packets from the caller, a DTLS error is generated. This results in the media session being torn down, which is followed by teardown at signaling (SIP) level too. Abuse of this vulnerability may lead to a massive Denial of Service on vulnerable FreeSWITCH servers for calls that rely on DTLS-SRTP. To address this vulnerability, upgrade FreeSWITCH to 1.10.11 which includes the security fix. The solution implemented is to drop all packets from addresses that have not been validated by an ICE check.

Weakness: CWE-703 (Improper Check or Handling of Exceptional Conditions)

## Which versions are affected by CVE-2023-51443?

It affects 1 product.


Products: Freeswitch Freeswitch.

## How do I fix CVE-2023-51443?

Upgrade to a fixed version.

## Is CVE-2023-51443 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2023-51443 exists.

## Other vulnerabilities in signalwire freeswitch

- [CVE-2026-49841](https://insights.sbomify.com/CVE-2026-49841/): FreeSWITCH: Pre-authentication heap buffer overflow in `mod_verto` HTTP POST body read (critical 9.8)
- [CVE-2019-19492](https://insights.sbomify.com/CVE-2019-19492/): Hardcoded credentials in n/a (critical 9.8)
- [CVE-2026-49840](https://insights.sbomify.com/CVE-2026-49840/): FreeSWITCH: Pre-authentication heap buffer overflow in libesl `Content-Length` parsing (critical 9.1)
- [CVE-2021-41145](https://insights.sbomify.com/CVE-2021-41145/): FreeSWITCH susceptible to Denial of Service via SIP flooding (high 8.6)
- [CVE-2026-45771](https://insights.sbomify.com/CVE-2026-45771/): Freeswitch Denial-of-Service in SIP PUBLISH Requests via XML Entity Expansion (high 7.5)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2023-51443 and fix it if it is affected.

What it is: CVE-2023-51443 is a high-severity vulnerability in signalwire freeswitch, published on 27 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-2023-51443 exists.

Affected product: signalwire freeswitch. 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-2023-51443/ (Markdown: https://insights.sbomify.com/CVE-2023-51443/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2023-51443
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2023-51443
- OSV: https://osv.dev/vulnerability/CVE-2023-51443

---
From sbomify Insights: https://insights.sbomify.com/CVE-2023-51443/
Summaries are generated and may contain mistakes; the official description above is the record.