CVE-2026-118263 in Echo
Summary
by MITRE • 10/28/2026
Echo is a Go web framework. From 5.0.0 until 5.4.1, Echo v5's BodyDump middleware can discard a BodyLimit overflow error for an unknown-length request when BodyDump's capture limit is below the BodyLimit threshold. BodyDump drains the remaining body while ignoring read errors and replaces it with the captured prefix, so an HTTP/1.1 chunked request can be truncated and processed successfully even though the original body exceeded the configured limit. Known-length requests rejected before BodyDump runs are unaffected, and the issue does not establish a general authentication bypass or denial of service. This issue is fixed in 5.4.1.
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Analysis
by VulDB Data Team • 10/28/2026
The Echo web framework for Go, specifically versions ranging from 5.0.0 through 5.4.1, contains a logic flaw within its BodyDump middleware that can lead to the bypass of configured request body size limits under specific conditions. This vulnerability arises when an HTTP/1.1 client sends a chunked transfer-encoded request with an unknown total length and where the content exceeds the limit defined by the BodyLimit configuration. In such scenarios, if the capture limit set for the BodyDump middleware is lower than the BodyLimit threshold, the framework fails to properly reject the oversized payload. Instead of terminating the connection or returning an error as intended by the security policy, the system processes the request successfully after truncating it.
The technical root cause lies in how the BodyDump middleware handles stream consumption during overflow events. When a body limit is exceeded, the middleware is designed to drain the remaining data from the request body to ensure proper connection state management before returning an error. However, within this draining process, read errors are silently ignored rather than propagated or handled as fatal conditions. Consequently, if BodyDump captures only a prefix of the oversized payload due to its own lower capture limit, it effectively truncates the stream and allows the underlying handler to proceed with partial data. This behavior contradicts the security expectation that exceeding the body size limit should result in immediate rejection of the entire request, regardless of whether the length is known or chunked.
From an operational impact perspective, this flaw primarily affects applications relying on strict payload size enforcement for security or resource management purposes. An attacker could potentially exploit this by sending large chunked requests with payloads that exceed the configured BodyLimit but are truncated to fit within the BodyDump capture limit. While this does not constitute a general authentication bypass nor does it directly cause a denial of service in the traditional sense, it undermines integrity controls and may lead to unexpected application behavior if handlers assume they have received complete data up to the allowed limit. The vulnerability is limited to unknown-length requests processed by BodyDump; known-length requests that are rejected prior to reaching this middleware remain unaffected, which narrows the attack surface but does not eliminate the risk for dynamic or streaming content types.
To mitigate this issue, organizations using Echo versions 5.0.0 through 5.4.1 should upgrade immediately to version 5.4.1 or later, where the logic has been corrected to ensure that body limit violations are properly enforced even during stream draining operations by BodyDump. For environments unable to patch immediately, administrators can consider adjusting middleware ordering to ensure BodyLimit checks occur before BodyDump execution, although this may not fully resolve issues with chunked encoding if the framework architecture processes them concurrently. Monitoring for unusually large HTTP requests that result in partial processing or unexpected handler invocations can also aid in detecting potential exploitation attempts of this logic flaw.
This vulnerability aligns with CWE-20 Improper Input Validation, as the application fails to correctly validate and constrain input data against defined security policies before processing. It also relates to ATT&CK technique T1568 Dynamic Resolution, where an attacker might use dynamic content delivery techniques like chunked encoding to evade static size-based detection mechanisms. By ensuring that all parts of the request pipeline enforce consistent limits regardless of transfer encoding or middleware capture configurations, developers can maintain robust input validation standards and prevent partial data processing from compromising application security posture.