CVE-2026-118653 in Echo
Summary
by MITRE • 10/28/2026
Echo is a Go web framework. From 4.0.0 until 5.1.0, Context.RealIP falls back to client-supplied X-Forwarded-For or X-Real-IP values when Echo.IPExtractor is unset, and the default RateLimiter uses that result as its client identifier. A remote attacker can rotate arbitrary forwarded-address values to obtain new rate-limit buckets and bypass IP-based throttling used for controls such as brute-force or request-volume protection. This issue is fixed in Echo v5.1.0.
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Analysis
by VulDB Data Team • 10/28/2026
The vulnerability identified within the Echo web framework, specifically affecting versions from 4.0.0 through 5.1.0, represents a critical flaw in how client identity is established for security controls such as rate limiting. The core of this issue lies in the behavior of the Context.RealIP method when the custom IP extractor function is not configured by the application developer. In these default configurations, Echo relies on standard HTTP headers like X-Forwarded-For and X-Real-IP to determine the originating client's IP address. While these headers are commonly used in production environments behind reverse proxies or load balancers to preserve original client information, they are inherently untrusted because their values can be easily manipulated by any remote actor sending an HTTP request directly to the application server.
The operational impact of this flaw is significant for applications that depend on IP-based throttling mechanisms to protect against abuse. The default RateLimiter implementation in Echo utilizes the result from Context.RealIP as the unique identifier for each client session or connection bucket. Because a remote attacker can arbitrarily set these header values, they are able to rotate their apparent source IP address with every request or at frequent intervals. This capability allows an adversary to bypass rate-limiting protections that are designed to mitigate brute-force attacks against authentication endpoints, prevent denial-of-service conditions by limiting request volume per client, and enforce fair usage policies on public APIs. Each new fake IP address is treated as a distinct user, thereby resetting the throttling counter and granting unlimited access relative to the configured limits.
This vulnerability aligns with CWE-295 Improper Certificate Validation in terms of trusting unverified input data for security decisions, but more specifically it maps to CWE-749 Exposed Dangerous Method or API if one considers the exposure of internal rate-limiting logic through misconfigured trust boundaries. In the context of the MITRE ATT&CK framework, this flaw facilitates techniques associated with Resource Hijacking and Defense Evasion, as attackers can evade detection systems that rely on static IP reputation or volume-based thresholds. The lack of validation for forwarded headers means the application fails to enforce a strict chain of trust regarding client identity, allowing adversaries to obscure their true origin and scale attacks without triggering protective measures.
To mitigate this vulnerability, organizations running Echo versions prior to 5.1.0 must upgrade immediately to version 5.1.0 or later where the issue has been resolved by implementing stricter validation logic for IP extraction. For environments that cannot yet upgrade, a temporary mitigation involves configuring a custom IP extractor function via Echo.IPExtractor. This custom implementation should ignore X-Forwarded-For and X-Real-IP headers unless they are validated against known proxy IPs defined in a trusted list. Alternatively, applications can rely solely on the direct connection remote address provided by the underlying HTTP server when running directly without an untrusted reverse proxy layer. Ensuring that rate-limiting identifiers are derived from immutable network-layer attributes rather than mutable application-layer headers is essential for maintaining robust security controls against automated abuse and brute-force attempts.