CVE-2026-50574: yt-dlp aria2c Arbitrary File Write and Code Execution

Technical summary

CVE-2026-50574 is an arbitrary file write vulnerability in yt-dlp stemming from insufficient input sanitization when passing arguments to aria2c as an external downloader. The vulnerability occurs specifically when processing fragmented manifest formats (HLS, DASH). An attacker can craft a malicious manifest or URL that, when processed by yt-dlp with aria2c enabled, results in unsanitized input being passed to aria2c, allowing file write operations outside the intended download directory. The underlying weakness is improper neutralization of special elements used in a command (CWE-74). The attack requires user interaction (clicking a link, downloading from an attacker-controlled source) and relies on the victim having configured aria2c as an external downloader, making exploitability conditional but not trivial to achieve.

Business impact

Organizations and individuals relying on yt-dlp for automated media workflows face significant risk if aria2c is configured as the external downloader. Content creators, researchers, and media operations that use yt-dlp in CI/CD pipelines or automation could inadvertently execute attacker-supplied code, leading to data exfiltration, supply chain compromise, or lateral movement. The Windows immediate-execution variant is particularly concerning for corporate environments, while non-Windows systems face deferred but still critical risk. The scope is cross-border; attackers need only host malicious content or intercept legitimate manifest URLs.

Affected systems

yt-dlp versions prior to 2026.06.09 are affected. Exposure is limited to deployments where aria2c has been explicitly configured as an external downloader. Systems using yt-dlp's default downloader or other external downloaders (wget, curl) are not vulnerable. All operating systems running vulnerable versions are at risk, though Windows sees immediate impact while Linux, macOS, and other platforms experience delayed impact until the next yt-dlp invocation.

Exploitability

Exploitation requires moderate complexity: an attacker must craft a malicious fragmented media manifest or control a source URL, and the victim must actively download from that source using yt-dlp with aria2c enabled. User interaction is mandatory (the user must initiate the download). However, once these conditions are met, the arbitrary file write is reliable, and Windows users face immediate code execution. The attack surface includes any public or semi-public video/audio source if an attacker can inject or replace manifest files. Given the specialization required (aria2c configuration), mass exploitation is unlikely, but targeted attacks against specific organizations or individuals remain practical.

Remediation

Update yt-dlp to version 2026.06.09 or later. Users unable to upgrade immediately should disable aria2c as an external downloader or avoid downloading from untrusted sources. Administrators should review deployment configurations to identify systems using aria2c with yt-dlp and prioritize patching those assets. Defense-in-depth measures include restricting yt-dlp execution in sandboxed environments and monitoring for suspicious file write operations in download directories.

Patch guidance

Verify and deploy yt-dlp version 2026.06.09 or higher across all systems running vulnerable versions. Patch priority should be highest for Windows systems and high for non-Windows systems. Verify the patch through the official yt-dlp repository. Validate that aria2c-related functionality operates normally post-patch and that existing download configurations continue to work as expected. Test with both simple and fragmented manifest formats to confirm the fix does not introduce regressions.

Detection guidance

Monitor for yt-dlp version numbers below 2026.06.09 in your environment via software inventory or endpoint detection tools. Look for process execution patterns where yt-dlp spawns aria2c with unusual or malformed arguments, particularly those containing file path separators or special characters that could indicate an exploit attempt. Log and alert on unexpected file writes to system directories or outside designated download folders from yt-dlp or aria2c processes. On Windows, monitor for unexpected code execution chains originating from yt-dlp or aria2c. Network-level detection is difficult since the vulnerability does not require external communication; focus on endpoint and process forensics.

Why prioritize this

This vulnerability merits immediate attention despite not yet being on the KEV list. The HIGH CVSS score (8.3) reflects high confidentiality, integrity, and availability impact. Windows systems face immediate arbitrary code execution risk, which is a critical concern for any organization. Even deferred execution on non-Windows systems is severe. The requirement for aria2c configuration limits the attack surface but does not eliminate it—aria2c is a common external downloader choice among power users and automation platforms. The combination of cross-boundary scope, high impact, and practical exploitability justifies urgent patching.

Risk score, explained

The CVSS 3.1 score of 8.3 (HIGH) reflects: Network attack vector (AV:N), high complexity but achievable (AC:H), no privileges required (PR:N), user interaction mandatory (UI:R), and changed scope (S:C) allowing impact beyond the immediate vulnerable component. All three impact categories (C:H, I:H, A:H) are rated high due to arbitrary file write leading to code execution. The complexity accounts for the requirement that aria2c be configured and a fragmented manifest be processed, but these do not significantly reduce real-world risk for affected users.

Frequently asked questions