Sentry Middleware Bypass via Tunnel Route: CWE-601 Access Control Failure

Vulnerability Summary: Sentry Middleware Bypass (Tunnel Route) Overview When using the Tunnel route, the option in the Sentry SDK allows the browser to send events directly to a custom server (e.g., ), thereby bypassing middleware. However, this feature contains a security flaw: when middleware is positioned before the route, attackers can bypass the middleware by constructing specific paths (such as or ), causing security mechanisms like session validation to fail. This vulnerability affects all organizations relying on Sentry middleware for security controls, particularly those using middleware as their sole security layer. --- Scope of Impact Affected Versions: Fixed Versions: Severity: CVSS Score: 7.5 (High) CVSS Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:L/A:N CWE ID: CWE-601 (Improper Restriction of Operations within the Bounds of a Memory Buffer / Incorrect Access Control) Affected Scenarios: 1. Middleware path is 2. Middleware path is (TurboPack builds) 3. Application middleware conflicts with the Tunnel route path (e.g., ) 4. Middleware serves as the only security layer (e.g., session validation) --- Remediation Official Patch: Upgrade to one of the following versions: > Note: The new matching rule only requires the Tunnel route to actually exist; no additional configuration is needed. Temporary Mitigation: 1. Set to a path that is hard to guess (e.g., ) 2. When using TurboPack builds, the default path is , which avoids conflicts 3. Enhance security controls at the routing or data layer (do not rely solely on middleware) --- References Sentry Documentation - Tunnel Route Configuration PR #24282 PR #24283 PR #24286 --- > ⚠️ No POC or exploit code is available.

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Sentry Middleware Bypass via Tunnel Route: CWE-601 Access Control Failure

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