legeling PromptHub up to 0.5.3 skills.ts input validation

Summaryinfo

A vulnerability was found in legeling PromptHub up to 0.5.3. It has been classified as critical. This issue affects some unknown processing of the file apps/web/src/routes/skills.ts. The manipulation leads to input validation. This vulnerability is listed as CVE-2026-42261. The attack may be initiated remotely. There is no available exploit. Upgrading the affected component is recommended.

Detailsinfo

A vulnerability was found in legeling PromptHub up to 0.5.3 and classified as critical. This issue affects an unknown code block of the file apps/web/src/routes/skills.ts. The manipulation with an unknown input leads to a input validation vulnerability. Using CWE to declare the problem leads to CWE-20. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly. Impacted is confidentiality, integrity, and availability. The summary by CVE is:

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.

It is possible to read the advisory at github.com. The identification of this vulnerability is CVE-2026-42261 since 04/26/2026. The exploitation is known to be easy. The attack may be initiated remotely. Technical details of the vulnerability are known, but there is no available exploit.

Upgrading to version 0.5.4 eliminates this vulnerability.

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Productinfo

Vendor

• legeling

Name

• PromptHub

Version

• 0.5.0
• 0.5.1
• 0.5.2
• 0.5.3

Website

• Product: https://github.com/legeling/PromptHub/

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