Bug 2521777 (CVE-2026-75931) - CVE-2026-75931 fast-uri: fast-uri: Host confusion via skipped IDN canonicalization
Summary: CVE-2026-75931 fast-uri: fast-uri: Host confusion via skipped IDN canonicaliz...
Keywords:
Status: NEW
Alias: CVE-2026-75931
Product: Security Response
Classification: Other
Component: vulnerability
Version: unspecified
Hardware: All
OS: Linux
high
high
Target Milestone: ---
Assignee: Product Security DevOps Team
QA Contact:
URL:
Whiteboard:
Depends On:
Blocks:
TreeView+ depends on / blocked
 
Reported: 2026-08-24 09:51 UTC by OSIDB Bzimport
Modified: 2026-08-28 03:24 UTC (History)
99 users (show)

Fixed In Version:
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Description OSIDB Bzimport 2026-08-24 09:51:25 UTC
fast-uri is a URI parser for Node.js. It canonicalizes a host to its ASCII form only when the input carries an explicit scheme, so a scheme-relative reference such as a host preceded by two slashes is returned with its host verbatim and no error set. As a result fast-uri's own entry points disagree with each other: parse, resolve, normalize, and equal can yield different hosts for the same input depending only on whether a scheme is written out, and equal can return opposite verdicts for the same pair of hosts. An application that extracts a host with fast-uri to check it against a policy list and then resolves the same reference can make its decision on one host while the destination is another, enabling host confusion and policy bypass. The affected versions are 2.4.2 up to but not including 2.4.5, 3.1.3 up to but not including 3.1.6, and 4.0.1 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which canonicalize the host consistently across the resolve path. Users should upgrade to a patched version.


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