CVE-2026-42261 Details
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 — a supported and documented configuration — this means any internet user who can register. This issue has been patched in version 0.5.4.
A server-side request forgery (SSRF) vulnerability has been identified in PromptHub versions 0.4.9 prior to 0.5.4. The issue arises in the authenticated endpoint POST /api/skills/fetch-remote, which fetches a user-supplied URL and reflects the response body back to the caller. The SSRF protection in place attempts to block private and loopback destinations but can be bypassed using alternate representations of IPv6 addresses. This allows access to any IPv4 address, including loopback and private ranges, via IPv4-mapped IPv6 in hex form. The vulnerability can be exploited by any authenticated user, and in deployments with registration allowed, by any internet user who can register.
Users can update to PromptHub version 0.5.4, where this vulnerability has been patched.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 11, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/legeling/PromptHub/security/advisories/GHSA-9fhh-fjfg-5mr6 | CISA-ADP | ExploitMitigationVendor Advisory |
| https://github.com/legeling/PromptHub/releases/tag/v0.5.4 | [email protected] | PatchProduct |
| https://github.com/legeling/PromptHub/security/advisories/GHSA-9fhh-fjfg-5mr6 | [email protected] | ExploitMitigationVendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-20 | Improper Input Validation | [email protected] |
| CWE-693 | Protection Mechanism Failure | [email protected] |
| CWE-918 | Server-Side Request Forgery (SSRF) | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| legeling prompthub | >= 0.4.9, < 0.5.4 |
CPE
Remediation
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Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 12, 2026 | Initial Analysis | [email protected] |
| May 11, 2026 | CVE Modified | CISA-ADP |
| May 8, 2026 | New CVE Received | [email protected] |