{"id":"CVE-2026-42261","summary":"PromptHub: Authenticated SSRF via IPv6 filter bypass in `POST /api/skills/fetch-remote`","details":"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.","aliases":["GHSA-9fhh-fjfg-5mr6"],"modified":"2026-07-15T01:48:57.269662738Z","published":"2026-05-08T03:11:25.305Z","database_specific":{"cna_assigner":"GitHub_M","cwe_ids":["CWE-20","CWE-693","CWE-918"],"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42261.json"},"references":[{"type":"WEB","url":"https://github.com/legeling/PromptHub/releases/tag/v0.5.4"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/42xxx/CVE-2026-42261.json"},{"type":"ADVISORY","url":"https://github.com/legeling/PromptHub/security/advisories/GHSA-9fhh-fjfg-5mr6"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-42261"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/legeling/prompthub","events":[{"introduced":"1a4770d027d5b4f1e0ba8ce8ac66823f756932b1"},{"fixed":"726ade73c3714d449f985fe5b70f50895a51fe45"}],"database_specific":{"cpe":"cpe:2.3:a:legeling:prompthub:*:*:*:*:-:*:*:*","extracted_events":[{"introduced":"0.4.9"},{"fixed":"0.5.4"}],"source":["AFFECTED_FIELD","CPE_RANGE","REFERENCES"]}}],"versions":["web-v0.5.3-fix.1","web-v0.5.3","v0.5.3-rebuild.6","v0.5.3-rebuild.5","v0.5.3-rebuild.4","v0.5.3-rebuild.3","v0.5.3-rebuild.2","v0.5.3-rebuild.1","v0.5.3","v0.5.2-rebuild.3","v0.5.2-rebuild.2","v0.5.2-rebuild.1","v0.5.2","v0.5.1","v0.5.0","v0.4.9"],"database_specific":{"source":"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-42261.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N"}]}