A vulnerability in the Streamlink CLI utility allows unauthenticated remote attackers to perform unauthorized local file disclosure by exploiting improper handling of cross-protocol redirects.

The vulnerability stems from the HTTPSession component failing to restrict cross-protocol redirects, which permits an attacker to redirect a legitimate HTTP/HTTPS request to a local file system path. Because the application processes these requests via the FileAdapter, the contents of the local file are returned to the attacker, impacting confidentiality.

The ability to read arbitrary local files poses a significant security risk, potentially leading to the exposure of sensitive configuration files, system credentials, or private user data. While the CVSS score of 6.5 reflects a Medium severity, the potential for unauthorized data exfiltration from the underlying host justifies prioritizing this update to prevent host compromise.

Immediate Action: Update the Streamlink package to version 8.6.0 or later to ensure the proper validation of redirect protocols.

Proactive Monitoring: Monitor system and application logs for unusual file access patterns or unexpected network requests originating from the Streamlink process.

Compensating Controls: Restrict the network access of systems running Streamlink using egress filtering to prevent the application from reaching untrusted or malicious remote servers.

Public Exploit Available: Unknown.

Organizations utilizing Streamlink should immediately upgrade to version 8.6.0 to eliminate the risk of local file disclosure. Given that this vulnerability allows for the bypassing of intended security controls via redirection, timely patching is essential to maintain the confidentiality of local system resources.