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CVE-2026-18446

CVE-2026-18446 · fast-uri vulnerable to host confusion via backslash authority introducer

This page contains facts from public vulnerability sources. Check the original advisory before updating.

fast-uri before 4.1.2, 3.1.5, and 2.4.4 requires a literal double forward slash to recognize a URI authority, so a reference that uses a backslash based introducer in place of it (backslash backslash, forward slash backslash, or backslash forward slash) is parsed with no authority and folds into the path. Node's native WHATWG URL parser instead treats a backslash as interchangeable with a forward slash for special schemes, so the two parsers extract different hosts from the same input. Applications that use fast-uri to enforce host based policy such as allowlists, SSRF filtering, or redirect validation before passing the same URL into Node's URL or fetch consumers can be steered to an unintended host. Upgrade to fast-uri 4.1.2, 3.1.5, or 2.4.4.

CVSS 7.5 · High · EPSS 0.2% · Fix available

Published
Updated

Stack: system · node

Affected products and versions

  • fast-uri

    Versions
    • ≥ 4.0.0, < 4.1.2: Affected (semver)
    • 4.1.2: Not affected (semver)
    • ≥ 3.0.0, < 3.1.5: Affected (semver)
    • 3.1.5: Not affected (semver)
    • ≥ 0, < 2.4.4: Affected (semver)
    • 2.4.4: Not affected (semver)

    Update to 2.4.4; Update to 3.1.5; Update to 4.1.2

  • node-ajv Debian:13

    Versions
    • 8.12.0~ds+~2.1.1-5
    • 8.17.1~ds+~3.0.1+~3.1.0-1
    • 8.17.1~ds+~3.0.1+~3.1.0-2
    • 8.17.1~ds+~3.0.1+~3.1.0-3
    • 8.17.1~ds+~3.0.1+~3.1.0-4
    • 8.18.0~ds+~cs6.1.1-1
    • 8.18.0~ds+~cs6.1.1-2
    • 8.20.0~ds+~cs6.1.3-1
    • 8.20.0~ds+~cs7.1.2-1
    • 8.20.0~ds+~cs7.1.3-1
    • 8.20.0~ds+~cs7.1.3-2
    • 8.20.0~ds+~cs7.1.3-3
    • 8.20.0~ds+~cs7.1.4-1
    • 8.20.0~ds+~cs7.1.5-1
    • 8.20.0~ds+~cs7.1.6-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-ajv Debian:14

    Versions
    • 8.12.0~ds+~2.1.1-5
    • 8.17.1~ds+~3.0.1+~3.1.0-1
    • 8.17.1~ds+~3.0.1+~3.1.0-2
    • 8.17.1~ds+~3.0.1+~3.1.0-3
    • 8.17.1~ds+~3.0.1+~3.1.0-4
    • 8.18.0~ds+~cs6.1.1-1
    • 8.18.0~ds+~cs6.1.1-2
    • 8.20.0~ds+~cs6.1.3-1
    • 8.20.0~ds+~cs7.1.2-1
    Affected ranges
    • ECOSYSTEM: < 8.20.0~ds+~cs7.1.3-1

    Update to 8.20.0~ds+~cs7.1.3-1

  • fast-uri npm

    Affected ranges
    • SEMVER: < 2.4.4

    Update to 2.4.4

  • fast-uri npm

    Affected ranges
    • SEMVER: ≥ 3.0.0, < 3.1.5

    Update to 3.1.5

  • fast-uri npm

    Affected ranges
    • SEMVER: ≥ 4.0.0, < 4.1.2

    Update to 4.1.2

  • node-ajv Ubuntu:18.04:LTS

    Versions
    • 5.0.0-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-ajv Ubuntu:20.04:LTS

    Versions
    • 6.10.2-1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-ajv Ubuntu:22.04:LTS

    Versions
    • 6.12.6-2
    • 6.12.6-3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-ajv Ubuntu:24.04:LTS

    Versions
    • 6.12.6-3
    • 8.12.0~ds+~2.1.1-4
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-ajv Ubuntu:26.10

    Versions
    • 8.17.1~ds+~3.0.1+~3.1.0-4build1
    • 8.20.0~ds+~cs6.1.3-1
    • 8.20.0~ds+~cs7.1.2-1
    • 8.20.0~ds+~cs7.1.3-1
    • 8.20.0~ds+~cs7.1.3-3
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

  • node-ajv Ubuntu:26.04:LTS

    Versions
    • 8.12.0~ds+~2.1.1-5
    • 8.17.1~ds+~3.0.1+~3.1.0-2
    • 8.17.1~ds+~3.0.1+~3.1.0-4build1
    Affected ranges
    • ECOSYSTEM: (−∞, +∞)

    No fix published

Original sources

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