Vulnerability in Fast-Uri
CVE-2026-18446
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.
Published · last modified .
CVSS v3 metric
CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N.
EPSS exploit prediction
EPSS: 0.004 (32.2th percentile), scored .
Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 32nd percentile — 32.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.
EPSS over last 30 days · oldest: 0.002 · newest: 0.004 · change: +0.002
Affected products
- Fast-Uri — versions 4.0.0, 4.1.2, 3.0.0
- Openjsf Fast-Uri
Weakness classification (CWE)
References
- ce714d77-add3-4f53-aff5-83d477b104bb (Vendor Advisory)
- ce714d77-add3-4f53-aff5-83d477b104bb (Vendor Advisory)
Frequently asked questions
- What is CVE-2026-18446?
- CVE-2026-18446 is a high-severity vulnerability in Fast-Uri, classified under CWE-436. CVSS score: 7.5/10. Published 2026-07-31.
- How severe is CVE-2026-18446?
- High severity. CVSS v3 base score is 7.5 out of 10.