The U.S. Cybersecurity and Infrastructure Security Agency (CISA) on Monday 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. As of writing, the GitHub project has more than 43,500 stars and has been forked over 7,900 times.

The vulnerability in question relates to CVE-2025-62593 (CVSS score: 9.4), which can result in remote code execution via web browsers like Mozilla Firefox and Apple Safari by means of a DNS rebinding attack.

“Due to the longstanding decision by the Ray Development team to not implement any sort of authentication on critical endpoints, like the /api/jobs & /api/job_agent/jobs/ has once again led to a severe vulnerability that allows attackers to execute arbitrary code against Ray,” according to an advisory shared by Ray maintainers in November 2025. “This time in a development context via the browsers Firefox and Safari.”

The issue, at its core, stems from insufficient controls against browser-based attacks, specifically scenarios where the User-Agent header can be modified.

“Combined with a DNS rebinding attack against the browser, and this vulnerability is exploitable against a developer running Ray who inadvertently visits a malicious website, or is served a malicious advertisement,” the project maintainers added.

It’s worth noting that the defect primarily impacts developers running development/testing environments with Ray. Should a targeted victim fall prey to a phishing attack, or be served a malicious ad, it can lead to the execution of arbitrary shell code on their machine.

The project maintainers also noted that the attack can also be extended to attack 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.