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

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Summary

CVECVE-2026-42261
StatePUBLISHED
AssignerGitHub_M
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-05-08 04:16:20 UTC
Updated2026-05-08 04:16:20 UTC
DescriptionPromptHub 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.

Risk And Classification

Primary CVSS: v3.1 7.1 HIGH from [email protected]

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

Problem Types: CWE-20 | CWE-693 | CWE-918 | CWE-20 CWE-20: Improper Input Validation | CWE-693 CWE-693: Protection Mechanism Failure | CWE-918 CWE-918: Server-Side Request Forgery (SSRF)

VersionSourceTypeScoreSeverityVector
3.1[email protected]Secondary7.1HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
3.1CNADECLARED7.1HIGHCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

CVSS v3.1 Breakdown

Attack Vector
Network
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
Low
Availability
None

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Legeling PromptHub affected >= 0.4.9, < 0.5.4 Not specified

References

ReferenceSourceLinkTags
github.com/legeling/PromptHub/security/advisories/GHSA-9fhh-fjfg-5mr6 [email protected] github.com
github.com/legeling/PromptHub/releases/tag/v0.5.4 [email protected] github.com
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