Microsoft Warns of Stealthy Outlook Vulnerability Exploited by Russian Hackers

Microsoft on Friday shared guidance to help customers discover indicators of compromise associated with a recently patched Outlook vulnerability.

Tracked as CVE-2023-23397, the critical flaw relates to a case of privilege escalation that could be exploited to steal NT Lan Manager hashes and stage a relay attack without requiring any user interaction.

The vulnerability was resolved by Microsoft as part of its Patch Tuesday updates for March 2023, but not before Russia-based threat actors weaponized the flaw in attacks targeting government, transportation, energy, and military sectors in Europe.

“While leveraging NTLMv2 hashes to gain unauthorized access to resources is not a new technique, the exploitation of CVE-2023-23397 is novel and stealthy,” Microsoft said.

The disclosure comes as the U.S. Cybersecurity and Infrastructure Security Agency released a new open source incident response tool that helps detect signs of malicious activity in Microsoft cloud environments.

Dubbed Untitled Goose Tool, the Python-based utility offers “Novel authentication and data gathering methods” to analyze Microsoft Azure, Azure Active Directory, and Microsoft 365 environments, the agency said.

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