CVE-2026-121431 in AzuraCast
Summary
by MITRE • 11/03/2026
AzuraCast before 0.24.0 contains a server-side request forgery vulnerability that allows station users with WebHooks permission to bypass the UserUrlFilter guard via the Mastodon, Telegram, GroupMe, and RadioReg connectors. Attackers can set instance_url, api, or webhookurl to internal addresses and trigger the webhook test endpoint to reach loopback, private-network, or cloud-metadata services.
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Analysis
by VulDB Data Team • 11/03/2026
The vulnerability identified in AzuraCast versions prior to 0.24.0 represents a critical server-side request forgery flaw that stems from insufficient validation of user-supplied input within specific integration connectors. The affected components include the Mastodon, Telegram, GroupMe, and RadioReg integrations, which are designed to facilitate external communication for radio station management. These modules contain logic that allows authenticated users possessing WebHooks permissions to configure connection parameters such as instance_url, api endpoints, or webhookurl fields without adequate sanitization or restriction checks against internal network addresses. This architectural oversight effectively bypasses the UserUrlFilter guard mechanism intended to prevent requests from being directed toward non-public resources.
From a technical perspective, the core issue lies in the application's failure to enforce strict allow-listing of destination hosts during the webhook testing phase. When an attacker with WebHooks permissions initiates a test request through any of the vulnerable connectors, the server processes the provided URL and attempts to establish an outbound connection. Because the validation logic is either absent or easily circumvented within these specific modules, the application does not reject requests targeting loopback interfaces such as 127.0.0.1, private network ranges like 192.168.x.x or 10.x.x.x, or cloud metadata endpoints typically accessible only from within the host environment. This behavior aligns with CWE-918, which classifies server-side request forgery as a vulnerability where a web application fetches a remote resource without validating the user-supplied URL, potentially allowing attackers to probe internal services that are not exposed to the public internet.
The operational impact of this flaw is significant for organizations deploying AzuraCast in cloud or private network environments. An attacker can leverage this capability to perform port scanning and service discovery against internal infrastructure components that would otherwise remain hidden from external threats. By systematically varying the target IP addresses within webhook test requests, an adversary can map out the internal network topology, identify running services on non-standard ports, and detect vulnerabilities in backend systems such as databases, administrative panels, or other microservices. Furthermore, if any of these internal services suffer from authentication bypasses or unauthenticated access flaws, the attacker could potentially escalate their privileges to gain unauthorized control over critical system components. This scenario is consistent with ATT&CK technique T1046, Network Service Discovery, which describes adversaries using techniques to identify hosts and services on a network for further exploitation.
Mitigation strategies must focus on immediate patching and enhanced input validation practices. The primary remediation step is to upgrade AzuraCast to version 0.24.0 or later, where the developers have addressed this flaw by strengthening the URL filtering logic across all affected connectors. For environments that cannot immediately update due to compatibility constraints, administrators should implement network-level controls such as firewall rules or reverse proxy configurations to restrict outbound connections from the application server to only known and necessary external domains. Additionally, deploying a web application firewall with specific rulesets designed to detect SSRF patterns can provide an additional layer of defense by blocking requests that attempt to access private IP ranges or cloud metadata endpoints. Regular security audits should also include testing for URL validation bypasses in all modules handling user-supplied URLs to ensure comprehensive protection against similar vulnerabilities.