Answer in brief
CVE-2026-76172 records a Unknown severity vulnerability in fast-uri vulnerable to host confusion via percent-encoded scheme normalization. The current sources do not mark it as known exploited. The current feed maps fast-uri/fast-uri (generic). Check affected ranges and fixed versions before updating.
Analysis pending evidence review
HOL Guard separates source facts from reviewed analysis. See the methodology.
A CVSS score is not reported in the current record. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.
Analysis status
Analysis pending evidence review
Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.
The current feed maps fast-uri/fast-uri (generic). Check affected ranges and fixed versions before updating.
| Package | Affected range | Fixed version |
|---|---|---|
| fast-uri/fast-urigeneric | >=2.3.1 <2.4.5 || >=3.0.0 <3.1.6 || >=4.0.0 <4.1.3 | 2.4.5, 3.1.6, 4.1.3 |
Published upstream
Aug 24, 2026
Evidence: source:cvelist:source_dates:source-dates:recordSource modified
Aug 24, 2026
Evidence: source:cvelist:source_dates:source-dates:recordFirst seen by HOL
Aug 24, 2026
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.
Quoted source text, attributed separately from HOL analysis.