Magnitude EK Expands Arsenal With PuzzleMaker Exploit Chain


The Magnitude exploit kit (EK) is now capable of targeting Chromium-based browsers running on Windows systems, security researchers with Avast warn.

Exploit kits such as Magnitude are known for expanding their arsenal with new browser or plugin exploits in a timely fashion, but for years they have mainly focused on Microsoft’s Internet Explorer and left other browsers aside.

This, however, changed when Magnitude added to its arsenal exploits for CVE-2021-21224 and CVE-2021-31956, two vulnerabilities that affect Google’s Chrome browser and Microsoft’s Windows platform, respectively.

CVE-2021-21224, which Google addressed in April, is a type confusion flaw in the V8 rendering engine that could lead to remote code execution (RCE). The bug was already exploited in attacks when fixes rolled out.

CVE-2021-31956, on the other hand, is an elevation of privilege (EoP) vulnerability that could allow attackers to escape Chrome’s sandbox and gain system privileges. When patched in June 2021, the security hole was being abused in attacks alongside CVE-2021-31955, another EoP flaw in Windows.

The two vulnerabilities were previously chained in malicious activity that Kaspersky named PuzzleMaker, but which couldn’t be attributed to any known adversary.

On Tuesday, Avast’s security researchers took to Twitter to raise the alarm on Magnitude now targeting the Chrome and Windows vulnerabilities in a new wave of attacks.

“The attacks we have seen so far are targeting only Windows builds 18362, 18363, 19041, and 19042 (19H1–20H2). Build 19043 (21H1) is not targeted. The exploit for CVE-2021-31956 contains hardcoded syscall numbers relevant just for these builds,” Avast said.

For the time being, the activity doesn’t appear to involve the use of a malicious payload, although it does lead to the victim’s Windows build number being exfiltrated.

Since Magnitude typically tests newly implemented exploits in this manner, it’s likely that malicious attacks will follow soon, likely deploying the Magniber ransomware, Avast also says.

First observed in 2017, Magniber was associated right from the start with Magnitude, and was believed to be developed by the EK’s maintainers.

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Ionut Arghire is an international correspondent for SecurityWeek.

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