CVE-2026-79671 in Ech0
Summary
by MITRE • 08/25/2026
Ech0 through 4.2.1 contains a server-side request forgery vulnerability in the validateWebhookURL function (webhook_setting_service.go), which only validates literal IP addresses via net.ParseIP() and fails to reject hostnames that DNS-resolve to private or internal IPs (e.g., 169.254.169.254.nip.io). An attacker with admin privileges can create a webhook with such a hostname to bypass validation and cause the server to make requests to internal services, cloud metadata endpoints, and private network resources. The issue is fixed in 4.4.3.
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Analysis
by VulDB Data Team • 08/25/2026
The vulnerability identified in Ech0 versions through 4.2.1 represents a critical server-side request forgery flaw located within the validateWebhookURL function found in webhook_setting_service.go. This security defect stems from an insufficient validation mechanism designed to prevent internal network access when configuring webhooks. The core technical failure lies in the reliance on net.ParseIP() for input sanitization, which strictly validates literal IP address formats but completely ignores domain name resolution behaviors. Consequently, while direct requests to private IP ranges are blocked, attackers can circumvent this control by supplying a hostname that resolves via DNS to an internal or restricted IP address. This specific bypass technique exploits the separation between syntactic validation of the URL string and semantic validation of the resolved destination, allowing malicious actors to redirect server-side HTTP requests toward sensitive infrastructure components such as cloud metadata endpoints like 169.254.169.254.nip.io or other private network resources that are not directly accessible from external networks but are reachable by the application server itself.
From an operational impact perspective, this vulnerability poses a severe risk to organizations running affected versions of Ech0. An attacker who has obtained administrative privileges can exploit this flaw to perform unauthorized internal reconnaissance and data exfiltration. By crafting webhook configurations that point to internal services, the attacker forces the vulnerable server to act as a proxy or pivot point for attacking other systems within the same network segment. This capability is particularly dangerous in cloud environments where instance metadata endpoints contain sensitive authentication credentials, IAM roles, and configuration details. Successful exploitation can lead to full compromise of underlying infrastructure, unauthorized access to internal databases, and potential lateral movement across the network perimeter. The severity is amplified by the fact that administrative privileges are often granted to trusted users or compromised service accounts, making this a high-impact privilege escalation vector if combined with other initial access techniques.
This vulnerability aligns closely with Common Weakness Enumeration CWE-918, which describes Server-Side Request Forgery (SSRF), specifically falling under the subcategory of weak URL validation that fails to check for private IP ranges after DNS resolution. In terms of offensive security frameworks, this exploit maps directly to MITRE ATT&CK technique T1557, known as Adversary-in-the-Middle or Lateral Tool Transfer via SSRF, where the attacker uses the compromised application to interact with internal resources that are otherwise isolated from external access. The failure to implement a comprehensive allow-listing strategy for hostnames and IP addresses represents a fundamental design flaw in input validation logic. To mitigate this risk effectively, organizations must upgrade immediately to version 4.4.3 or later where the issue has been resolved. For environments unable to patch instantly, defensive measures should include implementing strict DNS resolution checks that reject any hostname resolving to RFC1918 private IP ranges, deploying network-level controls such as egress filtering to block outbound requests from application servers to internal metadata endpoints and private subnets, and enforcing least-privilege principles for webhook configuration permissions.