Chinese espionage groups swarm to exploit triple-link chain of zero-days
At least four China-aligned espionage groups chained three zero-days in Chromium browsers and Windows ALPC for espionage since late August.
Proofpoint observed at least four state-aligned threat groups, starting with TA412/Violet Typhoon/APT31 on August 28, chaining three zero-days in the 'BlueMoon' exploit chain targeting Chrome, Chromium-based browsers and Microsoft Windows. The chain includes RCE flaws in Chromium's JavaScript engine (CVE-2026-85046, CVE-2026-87491) and a Windows Advanced Local Procedure Call privilege-escalation zero-day (CVE-2026-85880), enabling sandbox code execution, sandbox escape and system privileges. APT31 delivered the chain via phishing links to NGOs, mining and commodity trading firms in the US, installing a browser extension disguised as Google Gemini to surveil activity and steal credentials. Other groups (UNK_LateNight, UNK_DoubleCheck, UNK_QuietRacket) targeted US aerospace, Vietnamese manufacturing, and Indonesian and Singaporean organizations; fewer than 20 victims were directly observed but the true count is likely higher.
- BlueMoon chain: two Chromium V8 RCE zero-days plus Windows ALPC privilege escalation
- APT31 struck first on Aug 28; activity peaked Sept 2-3 before Chrome patching
- Phishing lures installed a malicious browser extension disguised as Google Gemini
- Four espionage groups targeted US, Vietnam, Indonesia and Singapore victims
- Proofpoint expects the kit to proliferate to more actors as patches roll out
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2026-85046 | 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. 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. | 8.8 | 1% | KEV PoC ×5 |
| massmultiple billions of users/installs (Chrome is the dominant desktop browser at roughly 65% market share, with an estimated 3+ billion active users, plus… | |
| CVE-2026-85880 | 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. 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. | 7.8 | <1% | KEV |
| mass≈100M+ Windows installations (Windows 10 1607–22H2 on consumer/enterprise endpoints plus widely deployed Windows Server 2012–2022) | |
| CVE-2026-87491 | 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. 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. | 8.8 | <1% | KEV |
| massbillions of installations (Chrome's install base exceeds 3 billion users) |
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Multiple China-aligned threat groups exploited the defects quickly to target various organizations. Proofpoint said the activity is ongoing and expects it to widen.
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Proofpoint researchers have spotted at least four state-aligned threat groups chain a trio of zero-day vulnerabilities to conduct espionage on various targets of interest to China’s government since late August.
The Chinese espionage group that Proofpoint tracks as TA412, also known as Violet Typhoon and APT31, struck first, exploiting the chain of vulnerabilities Aug. 28. At least three additional espionage threat groups followed suit, exploiting the same vulnerabilities in subsequent waves of attacks days later, researchers said.
The exploit chain Proofpoint calls BlueMoon targets Chrome, Chromium-based browsers and Microsoft Windows. It allows attackers to run code in the browser’s sandbox, escape the sandbox and gain system privileges to access a targeted machine, said Mark Kelly, staff threat researcher at Proofpoint.
“All three vulnerabilities were exploited before patches were available to the public,” he said.
The vulnerabilities include: CVE-2026-85046 and CVE-2026-87491, remote-code execution defects in the JavaScript engine for Chromium-based browsers; and CVE-2026-85880, a privilege-escalation zero-day that Microsoft disclosed Tuesday in Windows Advanced Local Procedure Call.
“While the V8 vulnerabilities were known and fixed in Chromium source code, they were not yet patched in the latest publicly available browsers at the time of the activity, meaning they effectively functioned as zero-days in those products,” Kelly said.
Proofpoint said the exploit kit developer likely reverse engineered the publicly available Chromium patches to weaponize the browser exploit chain during that gap.
With a limited group of organizations exposed to all three vulnerabilities, attackers moved quickly and likely rushed development to target a narrow pool of potential targets. “In all observed cases, the infrastructure used for exploit delivery was created on the same day as — or in the days immediately preceding — the associated campaigns,” Proofpoint wrote in a threat intelligence report.
APT31, a group that’s committed espionage on behalf of China’s Ministry of State Security, including seven Chinese nationals indicted by the Justice Department in 2024, dropped various lures containing the exploit chain loader in phishing emails targeting non-governmental organizations, mining companies and commodity trading firms in the United States.
The phishing link installed a malicious browser extension disguised as Google Gemini on targeted machines, enabling attackers to surveil browser activity, steal credentials and execute commands, according to Proofpoint.
Other distinct threat groups have also used the BlueMoon exploit chain with some slight technical changes and variances in targeting.
“Proofpoint observed BlueMoon usage as recently as Sept. 8,” Kelly said. “The activity peaked Sept. 2-3 immediately prior to the Chrome patch being released and has continued intermittently since then.”
A China-aligned espionage threat group Proofpoint tracks as UNK_LateNight targeted multiple U.S. aerospace companies Sept. 2. Researchers also that day observed UNK_DoubleCheck, a suspected espionage-motivated threat group targeting Vietnamese manufacturing organizations with emails from a compromised Southeast Asian government account.
Researchers said UNK_QuietRacket, another espionage group aligned with China, targeted government, consulting and financial sector organizations in Indonesia and Singapore Sept. 3.
Proofpoint has directly observed fewer than 20 organizations targeted globally thus far, but Kelly said the true number of impacted organizations is likely much higher.
While Proofpoint attributes most of the observed attacks to Chinese espionage groups, attackers of other origins and motivations could strike soon as well.
“Given its ease of adoption, we expect the exploit kit is likely to proliferate further and be adopted by additional espionage-motivated and financially motivated threat actors as patched versions are fully rolled out across all Chromium-based browsers,” Kelly said.
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