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CVE-2026-42261

7.1 · HIGH

PromptHub is an all-in-one AI toolbox for prompt, skill, and agent management.

Published May 8, 2026CWE-20EPSS 0.34%

Overview

CVE-2026-42261 is a high-severity vulnerability. It was published on May 8, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

Technical 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.

Remediation

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

References

GitHubgithub.com/legeling/PromptHub/releases/tag/v0.5.4GitHubgithub.com/legeling/PromptHub/security/advisories/GHSA-9fhh-fjfg-5mr6GitHubgithub.com/legeling/PromptHub/security/advisories/GHSA-9fhh-fjfg-5mr6

How CyberStrike helps

Frequently asked questions

What is CVE-2026-42261?

CVE-2026-42261 is a high-severity vulnerability. It was published on May 8, 2026 and has a CVSS 3.1 base score of 7.1 (HIGH).

How severe is CVE-2026-42261?

This vulnerability has a CVSS 3.1 base score of 7.1, rated HIGH. It can be exploited remotely over the network. Some level of privileges is required for exploitation.

How do I fix or remediate CVE-2026-42261?

Check the references section for vendor advisories, patches, and mitigation guidance. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.

How can CyberStrike help with CVE-2026-42261?

CyberStrike is an open-source, AI-augmented pentesting engine. Rather than flag a version number, it tests whether an issue like CVE-2026-42261 is actually reachable in your own applications and APIs, then verifies each finding before reporting it. That tells you if the weakness is a real, exploitable risk in your environment or a false positive you can safely deprioritize.

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