The flaw occurs in the outbound podcast and radio fetch paths of Koel prior to version 9.7.1. The application performs a one‑time host safety check but fails to re‑validate URLs after following redirects, allowing an attacker to craft a request that redirects to an internal address or exploits DNS rebinding attacks. Because the vulnerable functions return parsed or streamed response content, an authenticated user can retrieve data from internal services or cloud metadata, exposing sensitive internal information. This weakness is mapped to CWE‑918.

All Koel installations running any release older than 9.7.1 that expose the podcast or radio APIs (createPodcastChannel, createInternetRadioStation, refreshPodcasts, apiResource podcasts, radio/stations) are affected. The issue is fixed in the 9.7.1 release, so newer versions are no longer vulnerable.

The CVSS score of 7.1 indicates medium‑to‑high severity. Exploitation requires an authenticated user with the ability to invoke the vulnerable API endpoints; therefore the attack surface is limited to those who can access the application. EPSS information is not available, and the vulnerability is not listed in the CISA KEV catalog. Nevertheless, the capacity to reach internal endpoints poses a significant confidentiality risk, especially for production deployments exposed to untrusted users.