CVE-2026-57202 in Asterisk
Summary
by MITRE • 10/27/2026
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 authenticated Asterisk REST Interface (ARI) attacker with read-only privileges may use `setChannelVar` to execute write dialplan functions, including `FILE()` writes, even when `live_dangerously` in `asterisk.conf` is set to no. The Asterisk HTTP web server must be enabled and reachable, and the attacker must already have valid `read-only ARI credentials`. HTTP is disabled by default and binds only to 127.0.0.1 by default even when enabled. 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.
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Analysis
by VulDB Data Team • 10/27/2026
Asterisk serves as a widely deployed open-source private branch exchange and telephony toolkit that facilitates voice over IP communications through various interfaces including the Asterisk REST Interface or ARI. The vulnerability in question involves an authentication bypass mechanism within this interface, specifically affecting versions prior to 20.20.1, 21.12.3, 22.10.1, and 23.4.1, as well as Certified Asterisk releases 20.7-cert11 and 22.8-cert3. The core technical flaw lies in the improper authorization checks applied to specific API endpoints when accessed by users with read-only privileges. Specifically, an authenticated attacker possessing only read access rights can exploit the setChannelVar function to execute write dialplan functions that are normally restricted. This includes the ability to perform FILE writes, which allows for the creation or modification of files on the underlying operating system where Asterisk is running.
The operational impact of this vulnerability is significant because it effectively neutralizes a key security control designed to prevent dangerous operations within the telephony application layer. The configuration parameter live_dangerously in asterisk.conf is intended to restrict certain high-risk actions, yet this flaw allows an attacker with minimal privileges to bypass that restriction entirely. By leveraging setChannelVar, the adversary can manipulate channel variables and trigger dialplan functions that write data to disk. This capability enables potential remote code execution if crafted files are subsequently processed by Asterisk or other system components, leading to a complete compromise of the telephony server's integrity and confidentiality.
From an industry standard perspective, this vulnerability aligns with CWE-269 Improper Privilege Management as it allows a user with lower privileges to perform actions reserved for higher privilege levels. It also relates to CWE-732 Incorrect Permission Assignment for Critical Resource since the file write operations are not properly gated by the intended security policies. In terms of attack vectors, this falls under MITRE ATT&CK technique T1059 Command and Scripting Interpreter as it involves executing system-level commands via dialplan functions, and potentially T1083 File and Directory Discovery if used to enumerate sensitive files before writing malicious content.
The risk profile is mitigated by the default configuration settings of Asterisk which disable the HTTP server and bind any enabled instance strictly to the loopback address 127.0.0.1. This means that external network access requires explicit administrative action to enable ARI and expose it beyond localhost, reducing the likelihood of exploitation in standard deployments. However, for environments where remote management via ARI is required over a trusted or untrusted network, this vulnerability presents a critical risk if proper segmentation or additional authentication layers are not implemented.
To mitigate this issue, organizations must upgrade to Asterisk version 20.20.1 or later, including the specific certified releases mentioned above which contain patches for these authorization flaws. If upgrading is not immediately feasible, administrators should ensure that the HTTP server remains disabled unless absolutely necessary and verify that any exposed ARI endpoints are protected by strong network-level access controls such as firewalls restricting source IPs to only trusted management stations. Additionally, enforcing strict least-privilege principles on API credentials ensures that even if an attacker gains initial access, they lack the permissions required to trigger these specific dialplan functions without further exploitation steps.