CVE-2026-18446 (GCVE-0-2026-18446)

Vulnerability from cvelistv5 – Published: 2026-07-31 14:37 – Updated: 2026-07-31 17:47
VLAI
Title
fast-uri vulnerable to host confusion via backslash authority introducer
Summary
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.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator (v2.0.3)
CWE
  • CWE-436 - Interpretation Conflict
Assigner
References
Impacted products
Vendor Product Version
fast-uri fast-uri Affected: 4.0.0 , < 4.1.2 (semver)
Unaffected: 4.1.2 (semver)
Affected: 3.0.0 , < 3.1.5 (semver)
Unaffected: 3.1.5 (semver)
Affected: 0 , < 2.4.4 (semver)
Unaffected: 2.4.4 (semver)
Create a notification for this product.
Credits
alanturing881 mcollina UlisesGascon
Show details on NVD website
To clipboard 

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