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.
- BlueMoon chains CVE-2026-85046 (V8 type confusion), CVE-2026-87491 (V8 sandbox escape) and CVE-2026-85880 (Windows kernel LPE).
- V8 fixes existed in upstream Chromium source but not in Chrome stable, giving attackers an unusually exploitable patch gap.
- A China-aligned actor hit US NGOs, mining and commodity trading firms using internship, conference and rapport-building lures.
- Within days four espionage clusters, mostly China-linked, adopted BlueMoon; financially motivated adoption is expected.
- Patches leave BlueMoon artifacts (extensions, scheduled tasks, registry keys); re-scan endpoints and apply Proofpoint detections.
Vulnerabilities mentioned
All| CVE | Vulnerability | CVSS | EPSS | Signals | Published |
|---|---|---|---|---|---|
| CVE-2026-85046 | Actively Exploited V8 Type Confusion in Google Chrome (CVE-2026-85046) | 8.8 | 2% | KEVPoC ×6 | KEV |
| CVE-2026-85880 | Heap-Based Buffer Overflow in Windows ALPC Enables Local Privilege Escalation | 7.8 | <1% | KEV | KEV |
| CVE-2026-87491 | Actively Exploited Out-of-Bounds Write in Google Chrome V8 | 8.8 | 4% | KEV | KEV |
From the original article
4 min read at csoonline.com
A new exploit kit is revealing the perils of the “patch later” mentality. According to the Proofpoint Threat Research team, espionage-motivated threat actors are using a new malicious toolkit to chain together four separate Chrome browser and Microsoft Windows vulnerabilities to allow them to launch targeted spear phishing campaigns.
csoonline.com
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