Bug 2529156 (CVE-2026-86253)

Summary: CVE-2026-86253 h3: h3: Arbitrary File Read via Path Traversal
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedKeywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in h3, an npm package. An unauthenticated remote attacker can exploit this vulnerability by sending crafted requests to endpoints served by the `serveStatic()` function. On Node.js deployments, the `event.url.pathname` is not properly normalized, allowing percent-encoded dot segments to be decoded into directory traversal sequences without sanitization. This path traversal vulnerability enables the attacker to read arbitrary files outside the intended static directory, leading to information disclosure.
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Description OSIDB Bzimport 2026-09-06 12:11:33 UTC 
h3 (npm package) versions <= 2.0.1-rc.14 contain a path traversal vulnerability in serveStatic(). On Node.js deployments, event.url.pathname is not normalized, so percent-encoded dot segments (%2e%2e) are passed to decodeURI() and decoded to ../ sequences without sanitization. An unauthenticated remote attacker can send crafted requests to endpoints served by serveStatic() to read arbitrary files outside the intended static directory. Fixed in 1.15.6 and 2.0.1-rc.15.