CVE-2026-54494
Summary
Koel's outbound-URL guard App\Helpers\Network::isPublicHost() classifies an IP as "public" using PHP's filter_var($ip, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE). That flag set does not recognise IPv6 transition-address forms that embed a private/loopback/link-local IPv4: NAT64 well-known prefix 64:ff9b::/96 (RFC 6052) and 6to4 2002::/16 (RFC 3056). An address such as 64:ff9b::7f00:1 (= 127.0.0.1), 64:ff9b::a9fe:a9fe (= 169.254.169.254, the cloud metadata endpoint), or 2002:a00:1:: (= 10.0.0.1) is reported as a public address, so the guard returns true and Koel proceeds to fetch the URL.
The guard is the only SSRF defense in front of App\Values\Podcast\EpisodePlayable::createForEpisode(), which downloads a podcast episode with Http::sink($file)->get($url) and streams the response body back to the requesting user. Because an attacker fully controls the <enclosure url> of any RSS feed they host (and any authenticated user can subscribe to a feed), they can publish an enclosure whose hostname has an AAAA record that is a NAT64/6to4 wrapper of an internal IP. On hosts with NAT64 or 6to4/dual-stack routing (the standard configuration on IPv6-only AWS/GCP subnets and 6to4-relayed networks), the kernel routes the wrapper to the embedded IPv4, and Koel performs a full-read SSRF against the internal endpoint — returning the response body to the attacker.
This is a server-side request forgery with full response disclosure (CWE-918) against internal services and cloud instance metadata.
Vulnerable code
app/Helpers/Network.php — isPublicHost() (the literal-IP branch and the per-resolved-record branch use the identical predicate):
public function isPublicHost(string $host): bool
{
if (filter_var($host, FILTER_VALIDATE_IP)) {
return (
filter_var($host, FILTER_VALIDATE_IP, FILTER_FLAG_NO_PRIV_RANGE | FILTER_FLAG_NO_RES_RANGE) !== false
);
}
try {
$records = array_merge(dns_get_record($host, DNS_A) ?: [], dns_get_record($host, DNS_AAAA)
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Advisory coverage (1)
External references
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[](https://www.csirts.com/cve/CVE-2026-54494)