The US Cybersecurity and Infrastructure Security Agency (CISA) has told federal civilian agencies they have just three days, rather than the usual 14, to patch a critical vulnerability in Ray, a widely used open-source framework for scaling Python and machine-learning workloads. The flaw, tracked as CVE-2025-62593 and rated 9.4 out of 10 in severity, is being actively exploited and allows attackers using Firefox or Safari to achieve remote code execution on vulnerable Ray systems, potentially giving them a route into private corporate networks via developers' machines.

The bug exploits a weakness in how vulnerable Ray versions check browser requests, relying on a User-Agent header check that Firefox and Safari allow scripts to bypass; combined with DNS rebinding, this lets attackers reach local Ray services if a developer simply visits a malicious website or ad. Ray, now managed by the Linux Foundation's PyTorch Foundation and used by firms including Amazon, Apple and OpenAI, has over 237 million downloads and is reportedly used by 60 percent of Fortune 500 companies. The issue stems from Ray's historical lack of authentication on critical endpoints, an assumption that clusters would run in isolated networks; version 2.52.0 fixes the flaw and adds optional (but not default) token-based authentication.