CVE-2026-57194
Description
A flaw was found in Asterisk. An out-of-bounds write vulnerability in the chan_unistim channel driver allows a remote attacker to cause a Denial of Service (DoS) by crashing the Asterisk service. By sending a specially crafted network request to an exposed chan_unistim port, an attacker can overflow an internal memory buffer during dial digit processing. This flaw requires the chan_unistim module to be loaded and accessible, allowing an attacker to disrupt telephony operations.
Statement
This vulnerability is rated as Moderate severity because exploitation is restricted to a denial of service and requires specific configuration preconditions, including an active UNISTIM channel driver and valid device registration access. In standard deployments, the chan_unistim driver is not enabled unless legacy UNISTIM telephony hardware is explicitly supported. Additionally, successful exploitation requires network reachability to the UNISTIM UDP listener and valid provisioning paths to reach the dialing interface, limiting exposure in typical production environments.
Understanding the Weakness (CWE)
Integrity
Technical Impact: Modify Memory; Execute Unauthorized Code or Commands
Write operations could cause memory corruption. In some cases, an adversary can modify control data such as return addresses in order to execute unexpected code.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
Attempting to access out-of-range, invalid, or unauthorized memory could cause the product to crash.
Other
Technical Impact: Unexpected State
Subsequent write operations can produce undefined or unexpected results.
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