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BlueMoon

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Attackers are weaponizing the gap between Chromium fixes and Chrome patches

Espionage actors use the BlueMoon exploit kit to chain Chrome V8 and Windows kernel zero-days via spear phishing, gaining full admin on unpatched endpoints.

Proofpoint, working with Google Threat Intelligence Group, Microsoft Threat Intelligence Center and Volexity, reports that the BlueMoon exploit kit chains V8 type confusion CVE-2026-85046, V8 sandbox escape CVE-2026-87491 and Windows kernel LPE CVE-2026-85880, all rated high severity. The V8 flaws were fixed in upstream Chromium source but had not yet reached Chrome stable releases, creating a patch gap that attackers reverse-engineered and weaponized. A China-aligned state-sponsored actor used the kit from August 28 against a small number of US NGOs, mining and commodity trading firms via rapport-building spear phishing, and within days several mostly China-linked espionage clusters adopted BlueMoon. The chain yields full Windows admin privileges from a single phishing click; defenders should patch Chrome and Windows, apply Proofpoint detections and hunt for leftover artifacts.

CSO Onlineupdated · 12h agofirst · 4d agoExploit / PoC in the wild 20 sourcesCVE-2026-85046CVE-2026-87491CVE-2026-85880

Related CVEs

  • CVE-2026-874918.8<1%
    Actively Exploited Out-of-Bounds Write in Google Chrome V8
    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.
    · Google Chrome (V8 JavaScript engine; tracked by CISA as 'Google Chromium V8') prior to 153.0.8010.36 KEVmass
  • CVE-2026-850468.81%
    Actively Exploited V8 Type Confusion in Google Chrome (CVE-2026-85046)
    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.
    · Google Chrome prior to 152.0.7977.82 · Google Chromium V8 V8 engine versions bundled with Chrome prior to 152.0.7977.82 KEV PoC ×5mass
  • CVE-2026-858807.8<1%
    Heap-Based Buffer Overflow in Windows ALPC Enables Local Privilege Escalation
    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.
    · Microsoft Windows 10 1607, 1809, 21H2, 22H2 · Microsoft Windows Server 2012, 2016, 2019, 2022 KEVmass

Appears with

threat actor China-aligned espionage clusters 1organization commodity trading firms 1organization mining companies 1organization US NGOs 1product Chrome 1product Chromium 1product Windows 1vendor Chromium 1vendor Google Chrome 1vendor Google Threat Intelligence Group 1vendor Microsoft Threat Intelligence Center 1vendor Microsoft Windows 1vendor Proofpoint 1vendor Volexity 1victim commodity trading firms 1victim mining companies 1
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