--- title: Anthropic Filesystem MCP Server: Directory Access Bypass... description: A security researcher discovered a path validation vulnerability in Anthropic's filesystem MCP server that allowed AI systems like Claude to bypass directory... canonical: https://daily.dev/posts/anthropic-filesystem-mcp-server-directory-access-bypass-via-improper-path-validation-embrace-the--wnjryckvs twitter:card: summary_large_image twitter:site: @dailydotdev og:type: website og:site_name: daily.dev og:title: Anthropic Filesystem MCP Server: Directory Access Bypass via Improper Path Validation · Embrace The Red | daily.dev og:description: A security researcher discovered a path validation vulnerability in Anthropic's filesystem MCP server that allowed AI systems like Claude to bypass directory... og:url: https://daily.dev/posts/anthropic-filesystem-mcp-server-directory-access-bypass-via-improper-path-validation-embrace-the--wnjryckvs og:image: https://api.daily.dev/og/posts/WnjrYcKvs.png og:image:alt: Anthropic Filesystem MCP Server: Directory Access Bypass via Improper Path Validation · Embrace The Red 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. # Anthropic Filesystem MCP Server: Directory Access Bypass via Improper Path Validation · Embrace The Red **[Embrace The Red](https://daily.dev/sources/embracethered)** · 2 min read · 1 upvotes · 0 comments ## Summary A security researcher discovered a path validation vulnerability in Anthropic's filesystem MCP server that allowed AI systems like Claude to bypass directory access controls. The flaw used improper string prefix matching instead of proper path validation, enabling access to sibling directories with similar names. For example, if access was granted to '/mnt/finance/data', the system would also allow access to '/mnt/finance/data-archived'. The vulnerability was responsibly disclosed and has since been fixed in a rewritten version of the server. ## Full article daily.dev links to this article rather than hosting it. Read it at the original source: --- Tags: [#security](https://daily.dev/tags/security), [#vulnerability](https://daily.dev/tags/vulnerability), [#anthropic](https://daily.dev/tags/anthropic) [View this post on daily.dev](https://daily.dev/posts/anthropic-filesystem-mcp-server-directory-access-bypass-via-improper-path-validation-embrace-the--wnjryckvs) ```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":"Anthropic Filesystem MCP Server: Directory Access Bypass via Improper Path Validation · Embrace The Red","url":"https://daily.dev/posts/anthropic-filesystem-mcp-server-directory-access-bypass-via-improper-path-validation-embrace-the--wnjryckvs","mainEntityOfPage":{"@type":"WebPage","@id":"https://daily.dev/posts/anthropic-filesystem-mcp-server-directory-access-bypass-via-improper-path-validation-embrace-the--wnjryckvs"},"datePublished":"2025-08-03T08:37:58.438Z","dateModified":"2025-08-03T08:38:17.300Z","description":"A security researcher discovered a path validation vulnerability in Anthropic's filesystem MCP server that allowed AI systems like Claude to bypass directory...","image":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/5e826416752edbaae81a4c375b30bc79?_a=AQAEulh","thumbnailUrl":"https://media.daily.dev/image/upload/f_auto,q_auto/v1/posts/5e826416752edbaae81a4c375b30bc79?_a=AQAEulh","isAccessibleForFree":true,"articleSection":"Embrace The Red","inLanguage":"en","publisher":{"@type":"Organization","name":"daily.dev","url":"https://daily.dev","logo":{"@type":"ImageObject","url":"https://daily.dev/apple-touch-icon.png","width":180,"height":180}},"author":{"@type":"Organization","name":"Embrace The Red","logo":"https://media.daily.dev/image/upload/t_logo,f_auto/v1/logos/50e27c500f1444fd9ed7d91301ed2e9c","url":"https://daily.dev/sources/embracethered"},"commentCount":0,"discussionUrl":"https://daily.dev/posts/anthropic-filesystem-mcp-server-directory-access-bypass-via-improper-path-validation-embrace-the--wnjryckvs","interactionStatistic":[{"@type":"InteractionCounter","interactionType":{"@type":"LikeAction"},"userInteractionCount":1},{"@type":"InteractionCounter","interactionType":{"@type":"CommentAction"},"userInteractionCount":0}],"keywords":"security,vulnerability,anthropic","timeRequired":"PT2M"} {"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"name":"Home","item":"https://daily.dev"},{"@type":"ListItem","position":2,"name":"Embrace The Red","item":"https://daily.dev/sources/embracethered"},{"@type":"ListItem","position":3,"name":"Anthropic Filesystem MCP Server: Directory Access Bypass via Improper Path Validation · Embrace The Red"}]} ```