CISA warning: Serious Security Vulnerability in MS Sharepoint

Two security vulnerabilities in Sharepoint – both from last year – are currently causing trouble for Sharepoint administrators. Because attackers are increasingly exploiting a combination of the two vulnerabilities, the Cybersecurity Infrastructure Security Agency CISA is now also issuing a warning. Affected customers of the Greenbone Enterprise Feed have been warned since June 2023.

Remote Privilege Execution

The two vulnerabilities CVE-2023-29357 and CVE-2023-24955 together allow attackers to remotely gain administrator rights in a company’s SharePoint server. Details of the attack were published back in September 2023 at the Pwn2Own conference in Vancouver 2023 and can be found on the Singapore Starlabs blog, for example.

Massive attacks have now led to CISA recently issuing a warning about these vulnerabilities and including CVE-2023-29357 in its catalog of known exploited vulnerabilities. However, Greenbone has already had authenticated version checks for both CVEs since around June 2023 and an active check for CVE-2023-29357 since October 2023. Customers of the enterprise products have been receiving these CVEs as a threat for several months – in authenticated and unauthenticated scan mode.

Microsoft advises its customers on its website to update to the SharePoint Server 2019 version of June 13, 2023, (KB5002402), which fixes five critical vulnerabilities, including the first CVE mentioned by CISA. Furthermore, all administrators should install the antivirus software AMSI and activate Microsoft Defender in the SharePoint server. Otherwise, attackers could bypass authentication with fake authentication tokens and gain administrator rights.

Recognising and detecting vulnerabilities in the company at an early stage is important, as the many reports of damaging vulnerabilities show. Greenbone products can take on a lot of work here and ensure security – as a hardware- or as a virtual appliance. The Greenbone Enterprise Feed, which feeds all Greenbone security products, receives daily updates and therefore covers a high percentage of risks.