CVE-2026-42261

POST /api/skills/fetch-remote HTTP/1.1 Host: target.com Content-Type: application/json Authorization: Bearer <token> { "url": "http://[::ffff:7f00:1]:8080/admin" } # Explanation: The payload uses an IPv4-mapped IPv6 address in hex form (::ffff:7f00:1) to bypass the isPrivateIPv6 check and access the local loopback interface (127.0.0.1).

{"cve": {"id": "CVE-2026-42261", "sourceIdentifier": "[email protected]", "published": "2026-05-08T04:16:20.107", "lastModified": "2026-05-11T19:16:23.433", "vulnStatus": "Undergoing Analysis", "cveTags": [], "descriptions": [{"lang": "en", "value": "PromptHub is an all-in-one AI toolbox for prompt, skill, and agent management. From version 0.4.9 to before version 0.5.4, apps/web/src/routes/skills.ts exposes an authenticated endpoint POST /api/skills/fetch-remote that fetches a user-supplied URL server-side and reflects the response body (up to 5 MB) back to the caller. The SSRF protection in apps/web/src/utils/remote-http.ts (isPrivateIPv6) attempts to block private/loopback destinations, but multiple alternate-but-valid IPv6 representations bypass the check. The bypasses reach any IPv4 address (loopback, RFC1918, link-local) via IPv4-mapped IPv6 in hex form, and the canonical ::1 via any representation that isn't the literal string \"::1\". Any authenticated user (role: user or admin) can trigger the SSRF. On deployments configured with ALLOW_REGISTRATION=true — a supported and documented configuration — this means any internet user who can register. This issue has been patched in version 0.5.4."}], "metrics": {"cvssMetricV31": [{"source": "[email protected]", "type": "Secondary", "cvssData": {"version": "3.1", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N", "baseScore": 7.1, "baseSeverity": "HIGH", "attackVector": "NETWORK", "attackComplexity": "LOW", "privilegesRequired": "LOW", "userInteraction": "NONE", "scope": "UNCHANGED", "confidentialityImpact": "HIGH", "integrityImpact": "LOW", "availabilityImpact": "NONE"}, "exploitabilityScore": 2.8, "impactScore": 4.2}]}, "weaknesses": [{"source": "[email protected]", "type": "Secondary", "description": [{"lang": "en", "value": "CWE-20"}, {"lang": "en", "value": "CWE-693"}, {"lang": "en", "value": "CWE-918"}]}], "references": [{"url": "https://github.com/legeling/PromptHub/releases/tag/v0.5.4", "source": "[email protected]"}, {"url": "https://github.com/legeling/PromptHub/security/advisories/GHSA-9fhh-fjfg-5mr6", "source": "[email protected]"}, {"url": "https://github.com/legeling/PromptHub/security/advisories/GHSA-9fhh-fjfg-5mr6", "source": "134c704f-9b21-4f2e-91b3-4a467353bcc0"}]}}