Microsoft Defender Flaw Exploited to Deliver ACR, Lumma, and Meduza Stealers
Vulnerabilities mentionedAll →
| CVE | Vulnerability | CVSS | EPSS | Flags | Affected | Exposure | Published |
|---|---|---|---|---|---|---|---|
| CVE-2024-21412 | CVE-2024-21412: Security Feature Bypass in Microsoft Windows Internet Shortcut Files CVE-2024-21412 is a security feature bypass (CWE-693) in how Microsoft Windows handles Internet Shortcut files: a crafted shortcut can make Windows skip the security warning prompt that normally appears before untrusted internet content is opened or downloaded. Triggering it requires user interaction — an attacker must deliver a malicious shortcut file, typically via email or a malicious website, and convince the user to open it, which is reflected in the CVSS vector's UI:R component. An attacker who succeeds gains a bypass of those prompts, making it easier to retrieve and execute malicious remote content with fewer warnings; the DarkGate malware operators used exactly this technique in zero-day campaigns to distribute their loader. Anyone running the affected Windows 10 (1809, 21H2, 22H2), Windows 11 (21H2, 22H2, 23H2), Windows Server 2019, or Windows Server 2022 (including 23H2) builds was exposed. The flaw was patched in Microsoft's February 2024 Patch Tuesday release (2024-02-13), the same day CISA added it to the KEV catalog, and it is under active exploitation with known ransomware association and a 95.4% EPSS score. Do: Apply the February 2024 Windows cumulative security update (released 2024-02-13) or any later monthly cumulative update to every affected Windows 10, Windows 11, Windows Server 2019, and Windows Server 2022 build, and verify patch levels through your endpoint inventory. Because exploitation requires user interaction, as an interim control flag or block .url/Internet Shortcut attachments at email gateways and remind users not to open shortcuts from untrusted sources. Prioritize internet-facing and shared endpoints given the KEV listing and known ransomware use. | 8.1 | 95% | KEV ransomware |
| mass≈1 billion Windows 10/11/Server installations potentially affected worldwide (pre-patch installed base) |
Full article517 words · extracted from thehackernews.com · click to collapse
Ravie LakshmananJul 24, 2024Malvertising / Threat Intelligence
A now-patched security flaw in the Microsoft Defender SmartScreen has been exploited as part of a new campaign designed to deliver information stealers such as ACR Stealer, Lumma, and Meduza.
Fortinet FortiGuard Labs said it detected the stealer campaign targeting Spain, Thailand, and the U.S. using booby-trapped files that exploit CVE-2024-21412 (CVSS score: 8.1).
The high-severity vulnerability allows an attacker to sidestep SmartScreen protection and drop malicious payloads. Microsoft addressed this issue as part of its monthly security updates released in February 2024.
"Initially, attackers lure victims into clicking a crafted link to a URL file designed to download an LNK file," security researcher Cara Lin said. "The LNK file then downloads an executable file containing an [HTML Application] script."
The HTA file serves as a conduit to decode and decrypt PowerShell code responsible for fetching a decoy PDF file and a shellcode injector that, in turn, either leads to the deployment of Meduza Stealer or Hijack Loader, which subsequently launches ACR Stealer or Lumma.
ACR Stealer, assessed to be an evolved version of the GrMsk Stealer, was advertised in late March 2024 by a threat actor named SheldIO on the Russian-language underground forum RAMP.
"This ACR stealer hides its [command-and-control] with a dead drop resolver (DDR) technique on the Steam community website," Lin said, calling out its ability to siphon information from web browsers, crypto wallets, messaging apps, FTP clients, email clients, VPN services, and password managers.
It's worth noting that recent Lumma Stealer attacks have also been observed utilizing the same technique, making it easier for the adversaries to change the C2 domains at any time and render the infrastructure more resilient, according to the AhnLab Security Intelligence Center (ASEC).
The disclosure comes as CrowdStrike has revealed that threat actors are leveraging last week's outage to distribute a previously undocumented information stealer called Daolpu, making it the latest example of the ongoing fallout stemming from the faulty update that has crippled millions of Windows devices.
The attack involves the use of a macro-laced Microsoft Word document that masquerades as a Microsoft recovery manual listing legitimate instructions issued by the Windows maker to resolve the issue, leveraging it as a decoy to activate the infection process.
The DOCM file, when opened, runs the macro to retrieve a second-stage DLL file from a remote that's decoded to launch Daolpu, a stealer malware equipped to harvest credentials and cookies from Google Chrome, Microsoft Edge, Mozilla Firefox, and other Chromium-based browsers.
It also follows the emergence of new stealer malware families such as Braodo and DeerStealer, even as cyber criminals are exploiting malvertising techniques promoting legitimate software such as Microsoft Teams to deploy Atomic Stealer.
"As cyber criminals ramp up their distribution campaigns, it becomes more dangerous to download applications via search engines," Malwarebytes researcher Jérôme Segura said. "Users have to navigate between malvertising (sponsored results) and SEO poisoning (compromised websites)."
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