--- title: A Trailing Slash Bypassed AWS API Gateway Authorization description: A security researcher discovered that appending a trailing slash to AWS HTTP API paths bypasses Lambda authorizer authentication entirely. The root cause is a... canonical: https://daily.dev/posts/a-trailing-slash-bypassed-aws-api-gateway-authorization-xczhpumsq twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: A Trailing Slash Bypassed AWS API Gateway Authorization | daily.dev og:description: A security researcher discovered that appending a trailing slash to AWS HTTP API paths bypasses Lambda authorizer authentication entirely. The root cause is a... og:url: https://daily.dev/posts/a-trailing-slash-bypassed-aws-api-gateway-authorization-xczhpumsq og:image: https://api.daily.dev/og/posts/xCzhPuMsq.png og:image:alt: A Trailing Slash Bypassed AWS API Gateway Authorization og:image:width: 1200 og:image:height: 630 og:locale: en --- > ## Documentation Index > Fetch the complete documentation index at: https://daily.dev/llms.txt > Use this file to discover all available pages before exploring further. # A Trailing Slash Bypassed AWS API Gateway Authorization **[InfoQ](https://daily.dev/sources/infoq)** · 4 min read · 1 upvotes · 0 comments ## Summary A security researcher discovered that appending a trailing slash to AWS HTTP API paths bypasses Lambda authorizer authentication entirely. The root cause is a path normalization mismatch: HTTP API's greedy route matching layer and its authorization layer make independent decisions, and they disagree on what constitutes a path match. In a real fintech case, this allowed unauthenticated wire transfers. The fix involved switching to REST API (stricter path matching) and adding independent userId validation inside each Lambda function. A nearly identical vulnerability class appeared in gRPC-Go (CVE-2026-33186). Teams using HTTP API with Lambda authorizers should audit trailing-slash variants of protected routes and never rely solely on the authorizer to set authorization context fields. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: ## Similar posts on daily.dev - [How a software provider closed unknown paths to cloud compromise](https://daily.dev/posts/how-a-software-provider-closed-unknown-paths-to-cloud-compromise-dsptdwbqp) · CSO Online · 0 upvotes · 0 comments - [The Authorization Hole Nobody Noticed](https://daily.dev/posts/the-authorization-hole-nobody-noticed-b5cjqoqsw) · Larablog · 0 upvotes · 0 comments - [Everyone Knows About Broken Authorization – So Why Does It Still Work for Attackers?](https://daily.dev/posts/everyone-knows-about-broken-authorization-so-why-does-it-still-work-for-attackers--exddy4tnt) · Security Boulevard · 1 upvotes · 0 comments - [CVE-2025-64500: Incorrect parsing of PATH\_INFO can lead to limited authorization bypass \(Symfony Blog\)](https://daily.dev/posts/cve-2025-64500-incorrect-parsing-of-path-info-can-lead-to-limited-authorization-bypass-symfony-blo-cklstlu6z) · Symfony · 0 upvotes · 0 comments --- Tags: [#security](https://daily.dev/tags/security), [#aws](https://daily.dev/tags/aws), [#authentication](https://daily.dev/tags/authentication), [#aws-lambda](https://daily.dev/tags/aws-lambda) [View this post on daily.dev](https://daily.dev/posts/a-trailing-slash-bypassed-aws-api-gateway-authorization-xczhpumsq) ```json {"@context":"https://schema.org","@graph":[{"@type":"Organization","@id":"https://daily.dev/#organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180},"sameAs":["https://twitter.com/dailydotdev","https://github.com/dailydotdev","https://www.linkedin.com/company/daily-dev-ltd"]},{"@type":"WebSite","@id":"https://daily.dev/#website","url":"https://daily.dev","name":"daily.dev","publisher":{"@id":"https://daily.dev/#organization"},"potentialAction":{"@type":"SearchAction","target":{"@type":"EntryPoint","urlTemplate":"https://daily.dev/search?q={search_term_string}"},"query-input":"required name=search_term_string"}}]} {"@context":"https://schema.org","@type":"TechArticle","headline":"A Trailing Slash Bypassed AWS API Gateway Authorization","url":"https://daily.dev/posts/a-trailing-slash-bypassed-aws-api-gateway-authorization-xczhpumsq","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/a-trailing-slash-bypassed-aws-api-gateway-authorization-xczhpumsq"},"datePublished":"2026-06-01T10:10:10.545Z","dateModified":"2026-08-24T06:54:26.572Z","description":"A security researcher discovered that appending a trailing slash to AWS HTTP API paths bypasses Lambda authorizer authentication entirely. 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