CVE-2026-76172 (GCVE-0-2026-76172)

Vulnerability from cvelistv5 – Published: 2026-08-24 10:07 – Updated: 2026-08-24 14:29
VLAI
Title
fast-uri vulnerable to host confusion via percent-encoded scheme normalization
Summary
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.
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-24 14:29 UTC
CWE
  • CWE-177 - Improper Handling of URL Encoding (Hex Encoding)
Impacted products
Vendor Product Version CPE status
fast-uri fast-uri Affected: 2.3.1 , < 2.4.5 (semver)
Unaffected: 2.4.5 (semver)
Affected: 3.0.0 , < 3.1.6 (semver)
Unaffected: 3.1.6 (semver)
Affected: 4.0.0 , < 4.1.3 (semver)
Unaffected: 4.1.3 (semver)
guessed Create a notification for this product.
Show details on NVD website

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