CISA adds Microsoft Windows bugs to its Known Exploited Vulnerabilities catalog

CVE-2023-36025 is a security feature bypass in Windows SmartScreen in which a specially crafted file — exploited in the wild using Internet Shortcut (.url) files — evades the Mark-of-the-Web warning SmartScreen normally displays for content downloaded from the internet. The flaw is network-reachable and requires no authentication, but user interaction is required: it triggers when a user clicks the crafted file delivered via phishing email, chat, or a web download. By bypassing the SmartScreen prompt, the attacker removes a key user-facing defense that would otherwise flag or warn about the file, which facilitated delivery of malware in the observed DarkGate and Mispadu campaigns. Any unpatched Windows 10 (1507, 1607, 1809, 21H2, 22H2), Windows 11 (21H2, 22H2, 23H2), or Windows Server 2008/2012/2016/2019 system is affected, which at the time of disclosure effectively meant the entire supported Windows installed base. It is confirmed exploited in the wild: CISA added it to the KEV catalog on 2023-11-14, EPSS scores 30-day exploitation probability at 88.1% (100th percentile), though no public PoC is known.

Do: Apply Microsoft's November 2023 cumulative Windows security updates (the release containing the fix) on all affected Windows 10/11 and Windows Server systems; no configuration-based workaround is widely documented, so patching is the primary mitigation. Until patched, treat unexpected Internet Shortcut (.url) files arriving via email or chat with extra suspicion, since they can execute without the usual SmartScreen warning, and hunt for DarkGate/Mispadu indicators. Given the KEV listing and 88.1% EPSS, prioritize this fix in the current patch cycle; ransomware-associated use is reported as unknown.

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.