# CVE-2026-75899: fast-uri vulnerable to server-side request forgery via repeated hostname percent-decoding

> CVE-2026-75899: fast-uri vulnerable to server-side request forgery via repeated hostname percent-decoding. CVSS 7.5 (CVSS 3.1).

Canonical: https://rewindex.com/cve/CVE-2026-75899
Last updated: 2026-10-14T13:10:00Z

- Published: 2026-08-24 09:40 UTC · Updated: 2026-10-14 13:10 UTC · Assigner: openjs
- CVSS: 7.5 (CVSS 3.1) · Severity: High · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- EPSS: 0.22%, 12th percentile (scored 2026-10-25)
- CISA KEV: no
- CWE: CWE-174, CWE-918

## 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.

## Affected vendors and products

- fast-uri: fast-uri

## Tracked companies

- [Bitbucket](https://rewindex.com/company/bitbucket.md)
- [Jira](https://rewindex.com/company/jira.md)

## References

- [CVE record on cve.org](https://www.cve.org/CVERecord?id=CVE-2026-75899)
- [NVD entry](https://nvd.nist.gov/vuln/detail/CVE-2026-75899)
- [https://cna.openjsf.org/security-advisories.html](https://cna.openjsf.org/security-advisories.html)
- [https://github.com/fastify/fast-uri/security/advisories/GHSA-fph4-wmhf-6fwf](https://github.com/fastify/fast-uri/security/advisories/GHSA-fph4-wmhf-6fwf)

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_Sources: CVE records from the CVE Program (cve.org). CVE® is a registered trademark of The MITRE Corporation. (https://www.cve.org/) This product uses data from the NVD API but is not endorsed or certified by the NVD. (https://nvd.nist.gov/) Known Exploited Vulnerabilities catalog from CISA. (https://www.cisa.gov/known-exploited-vulnerabilities-catalog) EPSS scores from FIRST (Exploit Prediction Scoring System). (https://www.first.org/epss/)_


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Canonical: https://rewindex.com/cve/CVE-2026-75899 · Markdown: https://rewindex.com/cve/CVE-2026-75899.md · JSON: https://rewindex.com/api/v1/cves/CVE-2026-75899 · Data licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/) · Generated 2026-10-26T03:10:00.366Z