Bug 2556008 (CVE-2026-110180)

Summary: CVE-2026-110180 fast-uri: fast-uri: Security policy bypass via improper host canonicalization
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
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Priority: medium    
Version: unspecifiedKeywords: Security
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OS: Linux   
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A flaw was found in fast-uri. When processing web addresses, the host canonicalization mechanism can silently strip control characters or drop user information without verifying that the full host input was consumed. A remote attacker can exploit this parsing discrepancy by supplying a specially crafted address to bypass host-based security policies, such as domain blocklists, redirect validations, or proxy routing rules. As a result, applications may inadvertently direct network requests to unintended destinations.
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Description OSIDB Bzimport 2026-10-20 07:22:15 UTC 
fast-uri is a dependency-free RFC 3986 URI parser and serializer for Node.js. In versions from 2.4.2 through 2.4.7, from 3.1.3 through 3.1.8, and from 4.0.1 through 4.2.2, for HTTP-family schemes the canonicalizeHost() function passes the parsed host to the WHATWG URL parser and adopts its hostname without checking that the parser consumed the entire input as a host, so the authority can be silently rewritten: data before an at-sign is dropped and tab, carriage-return, and line-feed characters are stripped, with no error reported. An application that enforces host-based policy such as denylists, loopback filtering, redirect validation, or outbound proxy routing on one representation can then see the canonical host diverge from what it checked, allowing traffic to be steered to an unintended destination. The issue is fixed in fast-uri 2.4.8, 3.1.9, and 4.2.3, and users should upgrade to one of these versions or later. As a workaround, reject an authority that contains more than one at-sign or any tab, carriage-return, or line-feed before calling fast-uri, or treat any non-empty parse error as fatal and compare hosts only from the same parse result.