CISA Flags Actively Exploited Ray Flaw That Can Trigger Browser-Based RCE

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added a critical flaw impacting Ray to its Known Exploited Vulnerabilities (KEV) catalog, citing evidence of active exploitation.

The Hacker News 18 August 2026 Source: The Hacker News

The U.S. Cybersecurity and Infrastructure Security Agency (CISA) has added a critical flaw impacting Ray to its Known Exploited Vulnerabilities (KEV) catalog, citing evidence of active exploitation.

Ray is an open-source, Python-native distributed computing framework designed to scale artificial intelligence and machine learning workloads. It has a significant following, with over 43,500 stars on the GitHub project and more than 7,900 forks.

The vulnerability in question relates to CVE-2025-62593, which can result in remote code execution via web browsers like Mozilla Firefox and Apple Safari by means of a DNS rebinding attack. This is due to insufficient controls against browser-based attacks, specifically scenarios where the User-Agent header can be modified.

According to an advisory shared by Ray maintainers in November 2025, the issue stems from the decision not to implement any sort of authentication on critical endpoints. This has led to a severe vulnerability that allows attackers to execute arbitrary code against Ray, particularly in development contexts via the browsers Firefox and Safari.

The issue primarily impacts developers running development/testing environments with Ray. If a targeted victim falls prey to a phishing attack or is served a malicious ad, it can lead to the execution of arbitrary shell code on their machine.

The attack can also be extended to target network-adjacent instances of Ray by leveraging the browser as a confused deputy intermediary to target Ray instances running inside a private corporate network.

The issue has been addressed in version 2.52.0 of the Python package. Ray has credited Oligo security researcher Avi Lumelsky with discovering the fetch bypass and Jonathan Leitschuh for coming up with the DNS rebinding attack.

CISA has not shared any details of how the vulnerability is being exploited in the wild. However, a BitSight report from March 2026 revealed that the threat actors behind the RondoDox DDoS botnet had incorporated the vulnerability into their arsenal two days before it was publicly disclosed on November 26, 2025, because of the availability of a proof-of-concept (PoC) exploit.

According to Oligo, unpatched Ray instances have also been at the receiving end of cyber attacks that aim to turn infected clusters with NVIDIA GPUs into a self-replicating cryptocurrency mining botnet as part of a campaign dubbed ShadowRay 2.0.

In light of active exploitation of CVE-2025-62593, Federal Civilian Executive Branch (FCEB) agencies are recommended to apply necessary fixes and mitigations by August 20, 2026.