REDHAT-BUG-2521798: High severity npm/fast-uri vulnerability

Published Aug 24, 2026
·
Updated

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.

Affected Software

1 affected component
npm/fast-uri>=2.3.1<2.4.5, >=3.0.0<3.1.6, >=4.0.0<4.1.3

Remediation

Recommended actions to resolve this vulnerability, in priority order.

  1. Upgrade

    Upgrade fast-uri to a version that resolves this vulnerability.

    Fixed in 2.4.5
  2. Upgrade

    Upgrade fast-uri to a version that resolves this vulnerability.

    Fixed in 3.1.6
  3. Upgrade

    Upgrade fast-uri to a version that resolves this vulnerability.

    Fixed in 4.1.3

Event History

Aug 24, 2026
Data Sourced
via Red Hat·10:40 AM
DescriptionSeverityAffected Software

Contact

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