CVE-2026-75899
fast-uri vulnerable to server-side request forgery via repeated hostname percent-decoding
Description
fast-uri is a URI parser for Node.js. It decodes percent escapes in a hostname during parsing and then decodes the parsed hostname a second time during authority recomposition, so a single call to normalize or resolve can turn nested percent-encoded input into a different network destination such as a loopback hostname or address. For example, a doubly encoded host that spells out a loopback name decodes to that live host in one operation, which contradicts RFC 3986 section 2.4 that an implementation must not decode the same string more than once. An application that normalizes or resolves an untrusted HTTP-family URI before outbound routing, redirect validation, or a host-policy check can receive a destination different from the one the original encoded host represented, giving a server-side request forgery and host-policy bypass primitive. This is an incomplete-fix variant of CVE-2026-6322. The affected versions are 2.4.1 up to but not including 2.4.5, 3.1.2 up to but not including 3.1.6, and 4.0.0 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which normalize percent escapes once and preserve encoded percent signs. Users should upgrade to a patched version.
INFO
Published Date :
Aug. 24, 2026, 10:16 a.m.
Last Modified :
Aug. 24, 2026, 10:16 a.m.
Remotely Exploit :
No
Source :
ce714d77-add3-4f53-aff5-83d477b104bb
Affected Products
The following products are affected by CVE-2026-75899
vulnerability.
Even if cvefeed.io is aware of the exact versions of the
products
that
are
affected, the information is not represented in the table below.
No affected product recoded yet
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | ce714d77-add3-4f53-aff5-83d477b104bb |
Solution
- Upgrade to fast-uri version 2.4.5 or later.
- Upgrade to fast-uri version 3.1.6 or later.
- Upgrade to fast-uri version 4.1.3 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-75899.
| URL | Resource |
|---|---|
| https://cna.openjsf.org/security-advisories.html | |
| https://github.com/fastify/fast-uri/security/advisories/GHSA-fph4-wmhf-6fwf |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-75899 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-75899
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-75899 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-75899 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
New CVE Received by ce714d77-add3-4f53-aff5-83d477b104bb
Aug. 24, 2026
Action Type Old Value New Value Added Affected [{'vendor': 'fast-uri', 'product': 'fast-uri', 'versions': [{'status': 'affected', 'version': '2.4.1', 'lessThan': '2.4.5', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '2.4.5', 'versionType': 'semver'}, {'status': 'affected', 'version': '3.1.2', 'lessThan': '3.1.6', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '3.1.6', 'versionType': 'semver'}, {'status': 'affected', 'version': '4.0.0', 'lessThan': '4.1.3', 'versionType': 'semver'}, {'status': 'unaffected', 'version': '4.1.3', 'versionType': 'semver'}], 'packageURL': 'pkg:npm/fast-uri', 'defaultStatus': 'unaffected'}] Added Description fast-uri is a URI parser for Node.js. It decodes percent escapes in a hostname during parsing and then decodes the parsed hostname a second time during authority recomposition, so a single call to normalize or resolve can turn nested percent-encoded input into a different network destination such as a loopback hostname or address. For example, a doubly encoded host that spells out a loopback name decodes to that live host in one operation, which contradicts RFC 3986 section 2.4 that an implementation must not decode the same string more than once. An application that normalizes or resolves an untrusted HTTP-family URI before outbound routing, redirect validation, or a host-policy check can receive a destination different from the one the original encoded host represented, giving a server-side request forgery and host-policy bypass primitive. This is an incomplete-fix variant of CVE-2026-6322. The affected versions are 2.4.1 up to but not including 2.4.5, 3.1.2 up to but not including 3.1.6, and 4.0.0 up to but not including 4.1.3. The issue is fixed in 2.4.5, 3.1.6, and 4.1.3, which normalize percent escapes once and preserve encoded percent signs. Users should upgrade to a patched version. Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N Added CWE CWE-918 Added CWE CWE-174 Added Reference https://cna.openjsf.org/security-advisories.html Added Reference https://github.com/fastify/fast-uri/security/advisories/GHSA-fph4-wmhf-6fwf