A critical vulnerability, CVE-2025-53770, affects on-premises deployments of Microsoft SharePoint Server. The flaw stems from insecure deserialization of untrusted data, allowing unauthorized attackers to remotely execute arbitrary code over the network. Microsoft has confirmed that this vulnerability is actively being exploited in the wild. While a comprehensive security update is undergoing testing, Microsoft has issued interim mitigation guidance to reduce exposure. IONIX urges organizations to apply these mitigations immediately to protect vulnerable SharePoint instances from exploitation. Update (July 22nd): the IONIX research team developed an exploit simulation for relevant assets to verify whether the vulnerability can be exploited on those assets and assess potential exposure. The findings are detailed in this post.
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