{"uuid": "059bc356-2489-45d4-9070-7abe053ef9f2", "vulnerability_lookup_origin": "1a89b78e-f703-45f3-bb86-59eb712668bd", "author": "9f56dd64-161d-43a6-b9c3-555944290a09", "vulnerability": "CVE-2026-75931", "type": "seen", "source": "https://gist.github.com/alon710/6d6bc08cb0fafac0bb8a8c33b4c587ed", "content": "# CVE-2026-75931: CVE-2026-75931: Host Confusion and SSRF Bypass via Scheme-Relative URIs in fast-uri\n\n> **CVSS Score:** 7.5\n> **Published:** 2026-09-02\n> **Full Report:** https://cvereports.com/reports/CVE-2026-75931\n\n## Summary\nA host confusion vulnerability exists in the fast-uri Node.js library when parsing scheme-relative URI references. Due to inconsistent domain name canonicalization, applications validating resolved hosts can be bypassed by downstream WHATWG-compliant parsers, facilitating Server-Side Request Forgery (SSRF).\n\n## TL;DR\nA discrepancy in host canonicalization within fast-uri allows bypasses of SSRF and access-control filters when handling scheme-relative URI references.\n\n## Exploit Status: POC\n\n## Technical Details\n\n- **CWE ID**: CWE-436 (Interpretation Conflict)\n- **Attack Vector**: Network (AV:N)\n- **CVSS Score**: 7.5 (High)\n- **EPSS Score**: 0.00247 (15.89th percentile)\n- **Impact**: SSRF Filter Bypass / Host Obfuscation\n- **Exploit Status**: PoC / Conceptual\n- **CISA KEV Status**: Not Listed\n\n## Affected Systems\n\n- fast-uri (Node.js NPM package)\n- **fast-uri**: >= 2.4.2, < 2.4.5 (Fixed in: `2.4.5`)\n- **fast-uri**: >= 3.1.3, < 3.1.6 (Fixed in: `3.1.6`)\n- **fast-uri**: >= 4.0.1, < 4.1.3 (Fixed in: `4.1.3`)\n\n## Mitigation\n\n- Upgrade fast-uri to safe versions (2.4.5, 3.1.6, or 4.1.3)\n- Use native WHATWG URL parser to validate hostnames in security gateways\n- Force package resolutions/overrides for transitive fast-uri dependencies\n\n**Remediation Steps:**\n1. Identify and audit fast-uri versions inside node_modules and package lockfiles\n2. Run npm update fast-uri or yarn upgrade fast-uri to download fixed releases\n3. Implement package overrides or resolutions in package.json to pin secure versions\n4. Add WHATWG URL validation on policy enforcement checks as a defense-in-depth measure\n\n## References\n\n- [NVD Detail CVE-2026-75931](https://nvd.nist.gov/vuln/detail/CVE-2026-75931)\n- [GitHub Security Advisory GHSA-5jgf-p345-68v8](https://github.com/fastify/fast-uri/security/advisories/GHSA-5jgf-p345-68v8)\n- [Remediation Commit 4e4ebd](https://github.com/fastify/fast-uri/commit/4e4ebd8b245f6ca16e448203559eea3e545453a3)\n\n\n---\n*Generated by [CVEReports](https://cvereports.com/reports/CVE-2026-75931) - Automated Vulnerability Intelligence*", "creation_timestamp": "2026-09-02T16:31:29.955898Z"}