An exploit kit known as BlueMoon turns a single visit to a malicious website into full Windows malware execution by chaining two Google Chrome zero-days with a Windows kernel flaw, according to research published by Picus Security based on Proofpoint's investigation of the campaigns.

BlueMoon was first observed on 28 August 2026 and was adopted by four espionage-focused threat clusters between late August and early September, several of them with a suspected China nexus. Campaigns targeted the United States and Southeast Asia, including Vietnam, Indonesia and Singapore, across nonprofits, mining, commodity trading, aerospace, manufacturing, government, consulting and financial organisations.

The attack starts with a spearphishing email carrying a link to an attacker-controlled page. Some landing pages show a loading message while the exploitation runs, then redirect the visitor to a legitimate website. One cluster, tracked as TA412, sent fake conference emails titled "Keynote Speaker" to US nonprofits, mining companies and commodity traders, presenting the exploit page as conference details before redirecting visitors to a genuine academic site.

The chain itself has three links. CVE-2026-85046 creates type confusion in Chrome's V8 JavaScript engine, CVE-2026-87491 escapes the V8 sandbox, and CVE-2026-85880 escalates privileges in the Windows kernel, letting the kit inject code into the browser's parent broker process and run a payload outside the sandbox. Google patched the V8 flaws in September, and CISA added CVE-2026-87491 to its exploited-vulnerabilities catalogue on 9 September.

The payloads varied by campaign. TA412 delivered GemStone, a malicious browser extension posing as a Gemini browsing companion that collects keystrokes, cookies, browser storage and screenshots. Other campaigns delivered the ShadowPad backdoor, a Rust loader or custom malware with an in-memory .NET stage. The full chain works only on certain Windows builds, because the kernel exploit supported only older builds, so a vulnerable browser alone was not always enough for the attackers to succeed.