CVE-2025-49706: Microsoft SharePoint Improper Authentication Vulnerability

CVE-2025-49706 is an improper authentication vulnerability in Microsoft SharePoint that lets an authorized attacker perform spoofing over a network. Successful exploitation can let the attacker view sensitive information and make limited changes to it. The issue is known to be used in ransomware activity, can be chained with CVE-2025-49704, and has a related patch-bypass issue tracked as CVE-2025-53771; teams should treat it as high priority for any exposed SharePoint estate.

Because SharePoint often holds documents, lists, and collaboration data, a successful spoof can expand access or enable further abuse. Confirm all version and patch details against the current Microsoft advisory rather than relying on secondary summaries.

How it works

The weakness is classified as CWE-287 (Improper Authentication). In this class of flaw, authentication checks are incomplete or can be bypassed under certain conditions, allowing an already-authorized attacker to spoof identity or context over the network. The CISA summary states that successful exploitation of CVE-2025-49706 can permit viewing of sensitive information and some modification of disclosed data.

Public detail does not describe the exact request sequence or protocol fields involved; defenders should not invent exploit mechanics. The vulnerability can be chained with CVE-2025-49704. Separately, CVE-2025-53771 is described as a patch bypass for CVE-2025-49706, and the updates that address CVE-2025-53771 provide more robust protection than the earlier fixes for CVE-2025-49706 alone. Any technical investigation should therefore start from the latest vendor security update rather than older patches.

Am I affected? How to find it in your systems

Microsoft SharePoint is commonly deployed as on-premises SharePoint Server (often behind reverse proxies or load balancers) and may also appear in hybrid configurations. Inventory every SharePoint farm, web application, and site collection that is reachable from untrusted networks.

• Identify all SharePoint Server instances and record their build numbers and cumulative update levels; compare them to the fixed builds listed in the Microsoft advisory for CVE-2025-49706 and the related CVE-2025-53771.
• Flag any public-facing SharePoint Server that has reached end-of-life or end-of-service, including SharePoint Server 2013 and earlier versions; these must be treated as unsupportable.
• Review authentication and access logs for anomalous spoofing indicators such as unexpected identity claims, sudden privilege elevation within a session, or access to sensitive lists and document libraries from unusual source addresses. Correlate with any alerts that mention chaining to CVE-2025-49704.
• For cloud or hybrid services, confirm whether the environment falls under BOD 22-01 guidance and whether Microsoft has already applied the relevant service-side protections.

Exact affected version ranges and configuration prerequisites are not fully enumerated in the supplied facts; always verify against the vendor advisory before declaring a system safe.

How to remediate

Apply the Microsoft security updates that address both CVE-2025-49706 and the more robust protections included for the patch-bypass CVE-2025-53771. Prefer the latest cumulative update that Microsoft identifies as containing the complete fix set.

• Disconnect public-facing SharePoint Server instances that have reached end-of-life or end-of-service (explicitly including SharePoint Server 2013 and earlier) as required by CISA.
• For still-supported versions, follow the mitigations published by CISA and the vendor instructions; do not rely solely on the original CVE-2025-49706 patches if later updates for CVE-2025-53771 are available.
• After patching, re-validate authentication configuration, re-enable any temporarily disabled features only after testing, and confirm that the farm is no longer vulnerable by checking the installed update level against the advisory.
• If the product is used as a cloud service and mitigations are unavailable, adhere to BOD 22-01 guidance or discontinue use.

If you can't patch immediately

Until the vendor updates can be installed, reduce exposure with compensating controls that limit network reachability and increase detection.

• Immediately disconnect or place behind strong network controls any public-facing SharePoint Server that is end-of-life, including 2013 and earlier.
• Segment remaining SharePoint servers so that only authenticated management jump hosts and necessary internal clients can reach the authentication and content endpoints.
• Apply virtual patching or WAF rules that restrict anomalous authentication or spoofing patterns once the vendor or CISA publishes signatures; treat these as temporary only.
• Disable any non-essential authentication endpoints or features that the advisory indicates are involved, if operationally feasible.
• Heighten monitoring for the log and telemetry signs described above and alert on any chaining activity involving CVE-2025-49704. Prepare an isolation and forensic plan in case ransomware indicators appear.

If your data may have been exposed

Actively exploited vulnerabilities of this class, especially those with known ransomware use, frequently lead to data theft or encryption. If SharePoint content or credentials may have been accessed, treat the incident as a potential breach: isolate affected systems, preserve logs, and begin containment and recovery according to your incident-response plan. As a quick personal check, you can run a free exposure scan of your email address against known breach data sets to see whether related credentials have already appeared in public dumps.