Microsoft · SharePoint · Microsoft SharePoint Deserialization of Untrusted Data Vulnerability
Verdict
Patch first · actively exploited, reachable from the internet without credentials, and in the top 1% of CVEs by near-term exploitation probability
Added to CISA KEV 2025-07-20 · exploited in the wild for 434 days · used in ransomware campaigns
CVSS 9.8 CRITICAL. The score is a summary; these three components are the part that decides whether something scanning the internet can use it.
| Attack vector | networkreachable over the network, with no local access needed |
|---|---|
| Privileges required | noneneeds no credentials at all |
| User interaction | nonecan be triggered with nobody interacting with the page or request |
| Base vector | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H |
| Weakness | CWE-502 |
This describes the vulnerability. It says nothing about whether your systems run it.
EPSS puts the probability of exploitation in the next 30 days at 1.0000, which places it in the top 1% of all tracked CVEs. The percentile is the more useful half: 0.18 in absolute terms sounds low until you know most of the internet-facing software in the world scores under that.
| EPSS probability | 1.0000 |
|---|---|
| Percentile | 1.000 — top 1% |
| Added to KEV | 2025-07-20 |
|---|---|
| Days exploited | 434 |
| Federal remediation due | not set |
| Ransomware use | known to be used in ransomware campaigns |
Disconnect public-facing versions of SharePoint Server that have reached their end-of-life (EOL) or end-of-service (EOS) to include SharePoint Server 2013 and earlier versions. For supported versions, please follow the mitigations according to CISA (URL listed below in Notes) and vendor instructions (URL listed below in Notes). Adhere to the applicable BOD 22-01 guidance for cloud services or discontinue use of the product if mitigations are not available.
Deserialization of untrusted data in on-premises Microsoft SharePoint Server allows an unauthorized attacker to execute code over a network. Microsoft is aware that an exploit for CVE-2025-53770 exists in the wild. Microsoft is preparing and fully testing a comprehensive update to address this vulnerability. In the meantime, please make sure that the mitigation provided in this CVE documentation is in place so that you are protected from exploitation.