CVE-2026-6321
Path Normalization Bypass in fast-uri Library
Publication date: 2026-05-04
Last updated on: 2026-05-04
Assigner: openjs
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| fast-uri | fast-uri | to 3.1.0 (inc) |
| fast-uri | fast-uri | 3.1.1 |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-22 | The product uses external input to construct a pathname that is intended to identify a file or directory that is located underneath a restricted parent directory, but the product does not properly neutralize special elements within the pathname that can cause the pathname to resolve to a location that is outside of the restricted directory. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
This vulnerability exists in the fast-uri library versions up to 3.1.0. The issue is that the library decodes percent-encoded path separators and dot segments before applying dot-segment removal in its normalize() and equal() functions. Because encoded path data is treated like actual slashes and parent-directory references, different URIs that should be distinct can end up collapsing into the same normalized path.
As a result, applications that rely on normalizing or comparing attacker-controlled URLs to enforce path-based policies can be bypassed. An attacker can craft a path that appears to be confined under an allowed prefix but actually normalizes to a different location, potentially circumventing security controls.
How can this vulnerability impact me? :
The vulnerability can allow attackers to bypass path-based security policies by exploiting the way URLs are normalized. This means that an attacker could access resources or perform actions that should be restricted by the application’s URL path controls.
Since the CVSS score indicates a high impact on integrity (I:H) with no impact on confidentiality or availability, the main risk is unauthorized modification or manipulation of data or application behavior through crafted URLs.
What immediate steps should I take to mitigate this vulnerability?
To mitigate this vulnerability, update fast-uri to version 3.1.1 or later, as versions up to 3.1.0 are affected.