CVE-2025-53770 Microsoft SharePoint: unsafe data loading
In plain words: The program unpacks saved data from outside without checking it is safe. Usually lets an attacker run code on the server.
Confirmed exploited by CISA on · US federal patch deadline Jul 21, 2025
What to do
- Install Microsoft's security update for SharePoint. If no update exists, follow the vendor's workaround or stop using the product until one ships.
- Keep a list of every internet-facing server you run so nothing is forgotten.
- Patch anything in this catalog first, ahead of normal patch cycles.
- Put admin and file-transfer apps behind a VPN or single sign-on instead of the open internet.
Who is affected
Work IT. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.
What's at risk: Mass data theft and ransomware: a single flaw in a file-transfer or email server has exposed thousands of organisations at once.
The details
- Official name
- Microsoft SharePoint Deserialization of Untrusted Data Vulnerability
- Product
- Microsoft SharePoint
- CISA description
- Microsoft SharePoint Server on-premises contains a deserialization of untrusted data vulnerability that could allow an unauthorized attacker to execute code over a network. This vulnerability could be chained with CVE-2025-53771. CVE-2025-53770 is a patch bypass for CVE-2025-49704, and the updates for CVE-2025-53770 include more robust protection than those for CVE-2025-49704.
- Type of flaw
- Unsafe data loading (CWE-502)
- Confirmed exploited
- Jul 20, 2025 — known to be used in ransomware attacks
- US federal patch deadline
- Jul 21, 2025
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Answering about CVE-2025-53770 ·
Questions about CVE-2025-53770
Is CVE-2025-53770 being exploited?
Yes. CISA added CVE-2025-53770 to its Known Exploited Vulnerabilities catalog on Jul 20, 2025, which means there is reliable evidence of real-world attacks, including by ransomware groups.
How do I fix CVE-2025-53770?
Install Microsoft's security update for SharePoint. If no update exists, follow the vendor's workaround or stop using the product until one ships. Keep a list of every internet-facing server you run so nothing is forgotten.
Am I affected by CVE-2025-53770?
Only if you use Microsoft SharePoint. Aimed mostly at company systems — you are affected through the companies you use, not your own phone.