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Echo: BodyDump can discard BodyLimit overflow errors for unknown-length requests

Moderate severity GitHub Reviewed Published Oct 22, 2026 in labstack/echo • Updated Oct 28, 2026

Package

gomod github.com/labstack/echo/v5 (Go)

Affected versions

>= 5.0.0, < 5.4.1

Patched versions

5.4.1

Description

Impact

Echo v5's BodyDump middleware captured a bounded prefix, drained the remaining request body while ignoring read errors, and then replaced the body with the captured prefix. With an outer BodyLimit, an unknown-length request such as an HTTP/1.1 chunked request, and a BodyDump capture limit below the BodyLimit threshold, an overflow detected during that drain could be discarded.

The handler could consequently process a truncated request and return success even though the original body exceeded the configured limit. This is a conditional size-policy bypass; no general authentication bypass, production data modification or denial of service is claimed. Known-length requests rejected before BodyDump runs are unaffected by this path.

Affected versions and patch

All v5 releases from v5.0.0 through v5.4.0 contain the affected drain-and-replace logic. Runtime reproduction confirmed v5.4.0; source comparison confirms the same request handling in v5.0.0.

Upgrade to v5.4.1. BodyDump now captures only the configured prefix for logging and reconstructs the handler's reader from that prefix plus the unread original stream. It preserves the original closer and read errors instead of silently draining the rest. Fix commit.

Streaming BodyLimit enforcement still requires the application to consume the request body and handle read errors. The BodyDump capture cap is a logging cap, not an application body limit.

Workarounds

Disable BodyDump on affected routes, or ensure the BodyLimit overflow is detected during the initial capture by setting the capture limit above the enforced body limit. Upgrading is recommended because it also preserves the complete body for handlers.

Credits

Reported by @Duodum. The fix incorporates @jakezwang's request-body preservation work in #3105.

References

@vishr vishr published to labstack/echo Oct 22, 2026
Published to the GitHub Advisory Database Oct 23, 2026
Reviewed Oct 23, 2026
Last updated Oct 28, 2026

Severity

Moderate

CVSS overall score

This score calculates overall vulnerability severity from 0 to 10 and is based on the Common Vulnerability Scoring System (CVSS).
/ 10

CVSS v4 base metrics

Exploitability Metrics
Attack Vector Network
Attack Complexity Low
Attack Requirements Present
Privileges Required None
User interaction None
Vulnerable System Impact Metrics
Confidentiality None
Integrity Low
Availability None
Subsequent System Impact Metrics
Confidentiality None
Integrity None
Availability None

CVSS v4 base metrics

Exploitability Metrics
Attack Vector: This metric reflects the context by which vulnerability exploitation is possible. This metric value (and consequently the resulting severity) will be larger the more remote (logically, and physically) an attacker can be in order to exploit the vulnerable system. The assumption is that the number of potential attackers for a vulnerability that could be exploited from across a network is larger than the number of potential attackers that could exploit a vulnerability requiring physical access to a device, and therefore warrants a greater severity.
Attack Complexity: This metric captures measurable actions that must be taken by the attacker to actively evade or circumvent existing built-in security-enhancing conditions in order to obtain a working exploit. These are conditions whose primary purpose is to increase security and/or increase exploit engineering complexity. A vulnerability exploitable without a target-specific variable has a lower complexity than a vulnerability that would require non-trivial customization. This metric is meant to capture security mechanisms utilized by the vulnerable system.
Attack Requirements: This metric captures the prerequisite deployment and execution conditions or variables of the vulnerable system that enable the attack. These differ from security-enhancing techniques/technologies (ref Attack Complexity) as the primary purpose of these conditions is not to explicitly mitigate attacks, but rather, emerge naturally as a consequence of the deployment and execution of the vulnerable system.
Privileges Required: This metric describes the level of privileges an attacker must possess prior to successfully exploiting the vulnerability. The method by which the attacker obtains privileged credentials prior to the attack (e.g., free trial accounts), is outside the scope of this metric. Generally, self-service provisioned accounts do not constitute a privilege requirement if the attacker can grant themselves privileges as part of the attack.
User interaction: This metric captures the requirement for a human user, other than the attacker, to participate in the successful compromise of the vulnerable system. This metric determines whether the vulnerability can be exploited solely at the will of the attacker, or whether a separate user (or user-initiated process) must participate in some manner.
Vulnerable System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the VULNERABLE SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the VULNERABLE SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the VULNERABLE SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
Subsequent System Impact Metrics
Confidentiality: This metric measures the impact to the confidentiality of the information managed by the SUBSEQUENT SYSTEM due to a successfully exploited vulnerability. Confidentiality refers to limiting information access and disclosure to only authorized users, as well as preventing access by, or disclosure to, unauthorized ones.
Integrity: This metric measures the impact to integrity of a successfully exploited vulnerability. Integrity refers to the trustworthiness and veracity of information. Integrity of the SUBSEQUENT SYSTEM is impacted when an attacker makes unauthorized modification of system data. Integrity is also impacted when a system user can repudiate critical actions taken in the context of the system (e.g. due to insufficient logging).
Availability: This metric measures the impact to the availability of the SUBSEQUENT SYSTEM resulting from a successfully exploited vulnerability. While the Confidentiality and Integrity impact metrics apply to the loss of confidentiality or integrity of data (e.g., information, files) used by the system, this metric refers to the loss of availability of the impacted system itself, such as a networked service (e.g., web, database, email). Since availability refers to the accessibility of information resources, attacks that consume network bandwidth, processor cycles, or disk space all impact the availability of a system.
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N

EPSS score

Exploit Prediction Scoring System (EPSS)

This score estimates the probability of this vulnerability being exploited within the next 30 days. Data provided by FIRST.
(33rd percentile)

Weaknesses

Unchecked Return Value

The product does not check the return value from a method or function, which can prevent it from detecting unexpected states and conditions. Learn more on MITRE.

CVE ID

CVE-2026-118263

GHSA ID

GHSA-x9ff-22gv-65f4

Source code

Credits

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