← Vulnerability feed

Vulnerability record · CVE-2026-42261 · published 8 May 2026

CVE-2026-42261: Legeling prompthub improper input validation vulnerability

LLegeling · Prompthub

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.

7.1 CVSS 3.1 High EPSS 0.34% · top 75.0% CWE-20 · Improper input validationCWE-693 · CWE-693
7.1CVSS 3.1 base score
0.34%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
3References, 2 tagged exploit
17 Jun 2026Last modified by NVD

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.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/legeling/PromptHub/releases/tag/v0.5.4 PatchProduct
https://github.com/legeling/PromptHub/security/advisories/GHSA-9fhh-fjfg-5mr6 ExploitMitigationVendor Advisory
https://github.com/legeling/PromptHub/security/advisories/GHSA-9fhh-fjfg-5mr6 ExploitMitigationVendor Advisory

Track CVE-2026-42261 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.5CVE-2026-93952Arista velocloud orchestrator improper input validation vulnerabilityVeloCloud Orchestrator (VCO) on-prem has a security issue where this issue may allow a remote attacker to access privileged internal functionality an…KEVEPSS 0.90%8.8CVE-2019-1068Microsoft SQL Server improper input validation remote code executionMicrosoft SQL Server mishandles processing of internal functions, allowing an authenticated remote attacker to execute code on the database server. T…KEVEPSS 58%analysed5.9CVE-2025-68686FortiOS symbolic link patch bypass exposes sensitive informationFortiOS contains an information exposure flaw (CWE-200) that lets a remote unauthenticated attacker bypass the patch for the symbolic link persistenc…KEVEPSS 30%analysed9.3CVE-2026-12569PTC Windchill PDMlink and FlexPLM deserialization RCEPTC Windchill PDMlink and FlexPLM contain a deserialization of untrusted data flaw (also classified as improper input validation) that allows remote …KEVEPSS 46%analysed10.0CVE-2026-34910Ubiquiti UniFi OS input validation flaw allows command injectionUniFi OS devices contain an improper input validation vulnerability (CWE-20) that lets a network-reachable attacker inject and execute commands. It a…KEVEPSS 46%analysed7.2CVE-2026-6973Ivanti EPMM improper input validation enables remote code executionIvanti Endpoint Manager Mobile (EPMM) before versions 12.6.1.1, 12.7.0.1, and 12.8.0.1 contains an improper input validation flaw (CWE-20) that lets …KEVEPSS 2.5%analysed7.5CVE-2026-20133Cisco Catalyst SD-WAN Manager insufficient file system restrictions expose dataCisco Catalyst SD-WAN Software has insufficient file system restrictions that let an attacker read sensitive files on the underlying operating system…KEVEPSS 32%analysed8.8CVE-2026-34197Apache ActiveMQ Jolokia JMX bridge code injection via broker config URIApache ActiveMQ Classic exposes the Jolokia JMX-HTTP bridge at /api/jolokia/ with a default policy that allows exec operations on all org.apache.acti…KEVEPSS 15%analysed

Source: NIST National Vulnerability Database (record CVE-2026-42261), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.