Fastify fast-uri up to 2.4.7/3.1.8/4.2.2 URI Parser normalize/serialize path traversal

Summaryinfo

A vulnerability was found in Fastify fast-uri up to 2.4.7/3.1.8/4.2.2. It has been rated as problematic. The affected element is the function normalize/serialize of the component URI Parser. The manipulation leads to path traversal. This vulnerability is documented as CVE-2026-110095. The attack can be initiated remotely. There is not any exploit available. Upgrading the affected component is advised.

Detailsinfo

A vulnerability was found in Fastify fast-uri up to 2.4.7/3.1.8/4.2.2 and classified as problematic. This issue affects the function normalize/serialize of the component URI Parser. The manipulation with an unknown input leads to a path traversal vulnerability. Using CWE to declare the problem leads to 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. Impacted is integrity. The summary by CVE is:

fast-uri is a dependency-free RFC 3986 URI parser and serializer for Node.js. In versions before 2.4.8, from 3.0.0 through 3.1.8, and from 4.0.0 through 4.2.2, the normalize() and serialize() functions apply RFC 3986 dot-segment removal to the path of a relative-path reference, even though that algorithm is defined only for the merged target path during resolution, so a leading parent-directory segment can be dropped and a document-relative reference can become root-relative. An application that normalizes an attacker-supplied or user-supplied relative reference and then resolves it, or uses it as a cache, deduplication, or authorization key, can have the reference escape its intended directory and point at a different resource. The issue is fixed in fast-uri 2.4.8, 3.1.9, and 4.2.3, and users should upgrade to one of these versions or later. As a workaround, resolve a relative reference against its absolute base first and normalize the absolute result instead of normalizing the reference beforehand.

The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-110095 since 10/13/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Technical details are known, but no exploit is available. MITRE ATT&CK project uses the attack technique T1006 for this issue.

Upgrading to version 2.4.8, 3.1.9 or 4.2.3 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-104812). Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

Productinfo

Vendor

• Fastify

Name

• fast-uri

Version

• 2.4.0
• 2.4.1
• 2.4.2
• 2.4.3
• 2.4.4
• 2.4.5
• 2.4.6
• 2.4.7
• 3.1.0
• 3.1.1
• 3.1.2
• 3.1.3
• 3.1.4
• 3.1.5
• 3.1.6
• 3.1.7
• 3.1.8
• 4.2.0
• 4.2.1
• 4.2.2

Website

• Product: https://github.com/fastify/fast-uri/

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Several companies clearly confirm that VulDB is the primary source for best vulnerability data.

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