PromptHub: Authenticated SSRF via IPv6 filter bypass in `POST /api/skills/fetch-remote`_CVE-2026-42261

{
    "lastseen": "",
    "description": "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 \u2014 a supported and documented configuration \u2014 this means any internet user who can register. This issue has been patched in version 0.5.4.",
    "published": "2026-05-08T03:11:25.305Z",
    "modified": "2026-05-08T03:11:25.305Z",
    "type": "cve",
    "title": "PromptHub: Authenticated SSRF via IPv6 filter bypass in `POST /api/skills/fetch-remote`",
    "source": "GitHub_M",
    "references": "https://github.com/legeling/PromptHub/security/advisories/GHSA-9fhh-fjfg-5mr6\nhttps://github.com/legeling/PromptHub/releases/tag/v0.5.4",
    "id": "CVE-2026-42261",
    "bulletinFamily": "",
    "cwe": [
        "CWE-20",
        "CWE-693",
        "CWE-918"
    ],
    "cvelist": null,
    "sourceData": "legeling PromptHub >= 0.4.9, < 0.5.4",
    "sourceHref": "",
    "cvss": {
        "score": 7.1,
        "severity": "HIGH",
        "vector": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N",
        "version": "3.1"
    },
    "cvss2": [],
    "cvss3": {
        "version": "",
        "vectorString": "",
        "baseScore": 0,
        "baseSeverity": "",
        "attackVector": "",
        "attackComplexity": "",
        "privilegesRequired": "",
        "userInteraction": "",
        "scope": "",
        "confidentialityImpact": "",
        "integrityImpact": "",
        "availabilityImpact": "",
        "cvssV3": {
            "version": "",
            "vectorString": "",
            "baseScore": 0,
            "baseSeverity": "",
            "attackVector": "",
            "attackComplexity": "",
            "privilegesRequired": "",
            "userInteraction": "",
            "scope": "",
            "confidentialityImpact": "",
            "integrityImpact": "",
            "availabilityImpact": ""
        }
    },
    "href": "",
    "category_name": "CVE",
    "post_link": "",
    "product": "PromptHub",
    "version": ">= 0.4.9, < 0.5.4",
    "vendor": "legeling",
    "ai_description": "",
    "ai_severity": "",
    "ai_vendor": "",
    "ai_product": "",
    "ai_version": "",
    "ai_score": 0
}