BlueMoon Exploit Kit: China-Linked Espionage Groups Chain Chrome V8 and Windows Zero-Days

Google Chrome versions prior to 152.0.7977.82 contain a type confusion flaw (CWE-843) in the V8 JavaScript engine, which mishandles object types during engine operations (public proof-of-concept writeups indicate it is reachable through array sorting and WebAssembly-related code paths). A remote attacker triggers the flaw simply by getting a user to open a crafted HTML page, with no privileges or authentication required. Successful exploitation lets the attacker execute arbitrary code inside the browser's sandbox, and public reporting shows it being chained with Windows zero-days (the 'BlueMoon' exploit kit) by Chinese espionage groups for broader compromise. Any user of an unpatched Chrome or another build embedding the affected V8 engine is exposed. The vulnerability is a zero-day that was actively exploited in the wild before patching, was added to CISA's KEV on 2026-09-04, and has five public proof-of-concept references.

Do: Update Google Chrome to 152.0.7977.82 or later immediately, and apply the corresponding V8 fix in any Chromium-based browser in use. Federal agencies must apply mitigations in line with CISA BOD 26-04 and its cloud-services requirements, evaluating each asset's internet exposure. Because public reporting shows this flaw chained with Windows zero-days in 'BlueMoon' attacks, patch the related Windows vulnerabilities as well and hunt for signs of exploit-chain activity on high-exposure endpoints.

CVE-2026-85880 is a heap-based buffer overflow in Windows Advanced Local Procedure Call (ALPC), the Windows mechanism for local inter-process communication. An authorized local attacker can trigger the overflow by submitting crafted input over ALPC, corrupting heap memory in the component that handles the request. Successful exploitation allows the attacker to execute code with elevated privileges, typically gaining SYSTEM-level control of the local host, which is especially valuable as a post-exploitation or sandbox-escape step. Affected products include Windows 10 (1607, 1809, 21H2, 22H2) and Windows Server 2012, 2016, 2019, and 2022, meaning most on-premises Windows estates are in scope. The flaw was fixed in Microsoft's record 974-CVE September 2026 Patch Tuesday and was added to CISA's KEV on 2026-09-08, confirming exploitation in the wild; press reports describe Windows zero-days being chained with a Chrome zero-day in 'BlueMoon' kit attacks, though the data does not explicitly confirm this CVE is the Windows flaw in that chain.

Do: Apply Microsoft's September 2026 security (cumulative) updates for each affected Windows 10 and Windows Server build, as no public PoC or workaround is documented; CISA's KEV listing (added 2026-09-08) triggers BOD 26-04 patching requirements for federal agencies, so prioritize accordingly. Give priority to hosts where unprivileged users can log in — RDS/VDI servers, jump boxes, shared workstations — and to internet-exposed Windows servers, since an ALPC local privilege escalation is a common component in exploit chains combining remote code execution or browser flaws with elevation to SYSTEM. Organizations unable to patch promptly should follow BOD 26-04 guidance for cloud services or restrict local access to affected hosts until updates are applied.

CVE-2026-87491 is an out-of-bounds write (CWE-787) in the V8 JavaScript engine in Google Chrome, fixed in Chrome 153.0.8010.36, which Google shipped alongside roughly 230 other security fixes. An attacker can trigger the flaw remotely by luring a user (user interaction required) into opening a crafted HTML page that corrupts memory in V8. Successful exploitation allows the attacker to execute arbitrary code inside the Chrome browser sandbox, which constrains but does not eliminate the impact. All Google Chrome users running versions prior to 153.0.8010.36 are affected; because the flaw resides in V8, CISA tracks it as 'Google Chromium V8', and other Chromium-based browsers may inherit the fix in their own updates. The flaw is being actively exploited in the wild — it is the seventh actively exploited Chrome zero-day of 2026 and was added to CISA's KEV catalog on 2026-09-09 — though no public proof-of-concept is known and ransomware use is unknown.

Do: Update Google Chrome to 153.0.8010.36 or later immediately (open Help > About Google Chrome to force the update and relaunch), and verify the version on all endpoints. Also patch headless or automated Chrome deployments (CI runners, scrapers, kiosks, CDP-based tooling) that may lag auto-updates, and prioritize remediation per CISA KEV and BOD 26-04 requirements for federal systems. No public PoC is known and ransomware use is unknown, but confirmed in-the-wild exploitation warrants urgent patching.