CVE-2026-76172fast-uri vulnerable to host confusion via percent-encoded scheme normalization
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No exploitation reported and no EPSS estimate yet.
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fast-uri is a URI parser for Node.js. During parsing it runs a legacy decoding pass over the scheme component and never re-escapes the result, and serialization writes the scheme back out verbatim, unlike the host component which is re-escaped. As a result an input whose scheme carries percent-encoded slashes parses as a scheme with no authority, so the parsed host and error are both undefined, yet resolving or normalizing that same input emits a network-path reference whose authority is attacker-chosen and re-parses to that host. An application that allowlists on the parsed host, or treats a reference with no authority as safe to resolve against its base, gets the opposite of what it checked, giving an off-site redirect, server-side request forgery, or address-policy bypass. The legacy decoder also expands non-standard escape forms, widening the issue past upstream filters, and control characters in the scheme can reach the output as raw carriage return and line feed. The affected versions are 2.3.1 up to but not including 2.4.5, 3.0.0 up to but not including 3.1.6, and 4.0.0 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which reject a scheme that is not valid after decoding. Users should upgrade to a patched version.
- CVSS
- 7.5 HIGH (v3.1, CNA)CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- Weakness (CWE)
- CWE-177
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- openjs
- NVD analysis
- Analyzed
- Record last updated
- Aug 24, 2026
- First seen by InfoSec Signals
- Oct 9, 2026
Affected products
fast-uri fast-uri fast_uri:fast_uri (from the name) | from 2.3.1 before 2.4.5; 2.4.5 not affected; from 3.0.0 before 3.1.6; 3.1.6 not affected; from 4.0.0 before 4.1.3; 4.1.3 not affected | CNA record |
openjsf fast-uri openjsf:fast-uri | from 2.3.1 before 2.4.5; from 3.0.0 before 3.1.6; from 4.0.0 before 4.1.3 | NVD |
References
- https://github.com/fastify/fast-uri/security/advisories/GHSA-jqff-g426-hqxpvendor-advisory
- https://cna.openjsf.org/security-advisories.htmlvendor-advisory
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.