4 groups caught using the same Chrome and Windows exploit kit - Ars Technica

A patch gap and the hastened pace of AI-based vulnerability discovery are likely contributors.

A nearly identical exploit kit that targets critical vulnerabilities in both Chromium-based browsers and older versions of Windows is being actively used by at least four hacking groups, some of which have ties to the Chinese government.

Researchers from security firm Proofpoint said Wednesday that BlueMoon, the name they gave to the kit, chains three vulnerabilities together so the attackers using it can install malware of their choice. BlueMoon exploits two Chromium vulnerabilities and one in the kernel of Windows 10 (Oct. 2018 Update), Windows Server 2019, Windows 10 2004, Windows Server 2022, and the initial release of Windows 11. All three vulnerabilities have received patches in the past 24 hours.

The attacks lacked the stealth found in many campaigns. More often, hackers want to exploit newly discovered vulnerabilities sparingly to lengthen their longevity. Proofpoint hypothesized that one reason for the widely used and visible exploit chain was to take advantage of a “patch gap” in the Chromium supply chain, which spans the time a patch is available from developers and the time that patch is incorporated into browsers such as Chrome and Edge. Another likely contributor was the use of AI, which can often spot vulnerabilities faster than discovery performed solely by humans.

Both these factors likely pushed the attackers to move quickly before a window of opportunity closed. Proofpoint said:

A fully weaponized Chrome exploit chain has historically been a high-value, rare capability. BlueMoon was developed, deployed rapidly, and shared across multiple threat actors within days in a manner that had high detection signals. This may reflect a reduced cost and barrier to entry for this class of capability, as AI agents increasingly enable threat actor exploit development. This is particularly relevant for open source codebases, such as Chromium, where upstream patches are publicly accessible prior to downstream consumers of the codebase applying the patch. This creates a window for threat actors to attempt to rapidly reverse engineer patches and develop exploits ahead of downstream stable releases.

The four groups targeted a wide range of organizations and companies. The groups and targets included:

The first attack came from TA412 and began on August 28. The remainder began earlier this month. Proofpoint said it’s unknown if other groups also gained access to the exploit kit.

Both vulnerabilities targeting Chrome resided in V8, Google’s open source JavaScript engine. Exploiting a V8 type confusion bug and a separate sandbox escape in V8, the attackers were able to execute remote code. They then used a local privilege escalation in older versions of Windows to allow the malicious code to run with system rights. The first V8 vulnerability is tracked as CVE-2026-85046, and the Windows bug is tracked as CVE-2026-85880. Google doesn’t assign CVE designations for V8 sandbox escapes.

“Both V8 vulnerabilities were ‘patch-gap’ zero-days at the time of the observed activity,” Proofpoint said. “In other words, while they were known vulnerabilities already fixed in public upstream Chromium source code, they remained unpatched in the latest stable releases of Chrome and Chromium-based browsers available to the public. It is likely that the exploit kit developer used these publicly available Chromium patches to weaponize the browser exploit chain.”

Although BlueMoon leaves plenty of indications that it’s being used and all three vulnerabilities have been patched, Proofpoint said the kit may nonetheless continue to be used. “Given its ease of adoption, it is likely to proliferate further and be adopted by espionage-motivated and financially motivated threat actors as patched versions are fully rolled out across all Chromium-based browsers,” the researchers said.