CVE-2026-13676
HighCVSS 7.5Exploitation Probability (EPSS)
Low risk19th percentile - higher than 19% of all known CVEs
Summary
The vulnerability in fast-uri versions 2.3.1 through 3.1.2 and 4.0.0 fails to canonicalize Unicode (IDN) hostnames for HTTP-family URLs. The normalize() and equal() functions return values that differ from a WHATWG-compatible URL parser, allowing bypass of host-based security policies.
Risk Assessment
An organization can be tricked when an application uses fast-uri to validate hosts (e.g., domain denylists, loopback filtering, redirect validation) and then passes the same URL to Node.js URL or fetch, which interpret it differently. This leads to potential security bypass and unauthorized access.
Recommendation
Upgrade fast-uri to version 3.1.3 (for the 3.x line) or 4.0.1 (for the 4.x line) immediately. If an upgrade is not possible, enforce host policy using the same URL parser used for the actual request, or reject non-ASCII hosts before policy checks.
Original NVD description (English source)
fast-uri versions 2.3.1 through 3.1.2 and 4.0.0 fail to canonicalize Unicode (IDN) hostnames for HTTP-family URLs. The IDN conversion path calls a helper that does not exist on the global URL constructor, silently leaving the host in its original Unicode form while normalize() and equal() still return values that differ from a WHATWG-compatible URL parser. Applications that use fast-uri to enforce host-based policy (denylists, loopback filtering, redirect validation, outbound proxy routing) before passing the same URL to Node's URL or fetch can be bypassed when the two implementations resolve the same input to different hosts. Patches: upgrade to fast-uri 3.1.3 for the 3.x line or 4.0.1 for the 4.x line. Workarounds: enforce host policy using the same URL parser used for the actual request, or reject non-ASCII hosts before policy checks.