---
id: "CVE-2026-57194"
kind: "vulnerability"
aliases: ["CVE-2026-57194"]
title: "Asterisk: crafted UNISTIM packet overflows phone number field, crashing server"
severity: "medium"
cvss: 5.9
epss: null
exploited: false
status: "open"
category: "runtime"
products: []
ecosystems: []
tags: ["asterisk", "runtime", "self-hosted", "telephony", "unistim"]
not_affected_if: ["chan-unistim-not-loaded", "no-unistim-port-exposed"]
published_at: "2026-10-27T17:17:01+00:00"
first_seen_at: "2026-10-27T17:32:46+00:00"
updated_at: "2026-10-27T17:34:51+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-57194", "first_seen_at": "2026-10-27T17:32:46+00:00"}]
---

# Asterisk: crafted UNISTIM packet overflows phone number field, crashing server

Asterisk's chan_unistim module has an out-of-bounds write in DIALPAGE digit handling that overflows the phone_number field. A crafted incoming packet can crash Asterisk, causing a denial of service.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Check whether the `chan_unistim` module is loaded in Asterisk (for example with `asterisk -rx "module show like unistim"`).
- Check the Asterisk version with `asterisk -V` and compare it to the fixed releases.
- Check whether `unistim.conf` defines a UNISTIM UDP port reachable from untrusted networks.

## Fix

- Upgrade Asterisk to `20.20.1`, `21.12.3`, `22.10.1` or `23.4.1`.
- For Certified Asterisk, upgrade to `20.7-cert11` or `22.8-cert3`.
- If the UNISTIM module is not needed, unload or remove `chan_unistim`.

## Timeline

- 2026-10-27T17:32:46+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-57194

## From the sources

Asterisk is an open source private branch exchange and telephony toolkit. Prior to Asterisk 20.20.1, 21.12.3, 22.10.1, 23.4.1 and Certified Asterisk 20.7-cert11, 22.8-cert3, an out-of-bounds write in `chan_unistim` `DIALPAGE` digit handling can overflow the `phone_number` field and crash Asterisk when an attacker sends a carefully crafted incoming request packet. The `chan_unistim` module must be loaded and configured with a valid `UNISTIM UDP port` that the attacker can reach. The attacker must register as a configured `phone MAC`, or the deployment must have an equivalent `production/autoprovisioning` path that allows the client to reach the main page. This issue is fixed in Asterisk 20.20.1, 21.12.3, 22.10.1, 23.4.1 and Certified Asterisk 20.7-cert11, 22.8-cert3.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_