CVE-2026-79671 Overview
CVE-2026-79671 is a Server-Side Request Forgery (SSRF) vulnerability [CWE-918] in Ech0 versions through 4.2.1. The flaw resides in the validateWebhookURL function within webhook_setting_service.go. The function validates only literal IP addresses using Go's net.ParseIP() and does not resolve hostnames before allow-listing. An authenticated administrator can register a webhook whose hostname resolves via DNS to internal or reserved addresses, such as 169.254.169.254.nip.io. The server then issues outbound requests to internal services, cloud metadata endpoints, and private network resources. The maintainers fixed the issue in Ech0 4.4.3.
Critical Impact
An admin-level attacker can pivot the Ech0 server into internal networks and reach cloud instance metadata services, potentially exposing IAM credentials.
Affected Products
- Ech0 versions up to and including 4.2.1
- Ech0 deployments exposing the webhook settings API
- Fixed in Ech0 4.4.3
Discovery Timeline
- 2026-08-25 - CVE-2026-79671 published to NVD
- 2026-08-27 - Last updated in NVD database
Technical Details for CVE-2026-79671
Vulnerability Analysis
Ech0's webhook configuration workflow accepts a user-supplied URL and passes its host component through validateWebhookURL. The function's intent is to block requests targeting private, loopback, and link-local IP ranges. However, validation relies exclusively on net.ParseIP(), which returns a non-nil value only for literal IPv4 or IPv6 addresses. Hostnames pass validation unchecked because net.ParseIP() returns nil for any DNS name.
Once the webhook is saved, Ech0's HTTP client resolves the hostname at request time and issues the outbound call. Public DNS wildcards such as nip.io, sslip.io, and attacker-controlled authoritative servers can return arbitrary A records, including 169.254.169.254, 127.0.0.1, or RFC1918 addresses. The vulnerability enables reads against AWS, Azure, and GCP metadata endpoints and reconnaissance of internal HTTP services.
Root Cause
The root cause is incomplete input validation. net.ParseIP() cannot detect DNS-based bypasses because it never performs name resolution. A correct implementation must resolve the hostname, iterate over all returned addresses, and reject the request if any resolved IP falls within a disallowed range. Ech0 also lacked TOCTOU protections that would pin the resolved address between validation and connection.
Attack Vector
Exploitation requires administrative access to Ech0's webhook settings. The attacker creates a webhook pointing to a hostname engineered to resolve to an internal address. When Ech0 triggers the webhook, the server sends a request to the target internal endpoint and may return response data or side-channel signals to the attacker. Refer to the VulnCheck SSRF Advisory and the GitHub Security Advisory for full technical detail.
Detection Methods for CVE-2026-79671
Indicators of Compromise
- Webhook configurations referencing DNS wildcard services such as nip.io, sslip.io, or xip.io.
- Outbound HTTP requests from the Ech0 host to 169.254.169.254, metadata.google.internal, or RFC1918 ranges.
- Unexpected administrative changes to the webhook settings table in the Ech0 database.
Detection Strategies
- Inspect the Ech0 application log for webhook creation events and correlate the target hostname against DNS resolutions on the host.
- Alert on any process on the Ech0 server making requests to cloud metadata IP addresses.
- Review admin account activity for webhook additions that occurred outside normal change windows.
Monitoring Recommendations
- Enable egress logging on the Ech0 host and forward flow logs to a centralized analytics platform.
- Monitor DNS query logs for resolutions to link-local or private ranges initiated by the Ech0 service account.
- Track configuration changes to webhook_setting_service.go behavior via file integrity monitoring on the binary.
How to Mitigate CVE-2026-79671
Immediate Actions Required
- Upgrade Ech0 to version 4.4.3 or later, which enforces DNS resolution before validation.
- Audit existing webhook entries and remove any hostname that resolves to private, loopback, or link-local addresses.
- Rotate any cloud IAM credentials that were accessible from the Ech0 host's instance metadata service.
Patch Information
The maintainers of Ech0 addressed CVE-2026-79671 in release 4.4.3. The fix resolves the hostname prior to validation and rejects URLs whose resolved addresses fall in disallowed ranges. Details are published in the GitHub Security Advisory GHSA-r2x7-427f-rq69.
Workarounds
- Restrict administrative access to Ech0 using multi-factor authentication and network allow-lists.
- Deploy Ech0 behind an egress proxy that blocks requests to RFC1918, loopback, and link-local ranges.
- On AWS, enforce IMDSv2 with hop limit 1 to prevent SSRF-based credential theft from the instance metadata service.
# Configuration example: block SSRF egress at the host firewall
iptables -A OUTPUT -m owner --uid-owner ech0 -d 169.254.169.254 -j REJECT
iptables -A OUTPUT -m owner --uid-owner ech0 -d 10.0.0.0/8 -j REJECT
iptables -A OUTPUT -m owner --uid-owner ech0 -d 172.16.0.0/12 -j REJECT
iptables -A OUTPUT -m owner --uid-owner ech0 -d 192.168.0.0/16 -j REJECT
iptables -A OUTPUT -m owner --uid-owner ech0 -d 127.0.0.0/8 -j REJECT
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
