CyberSecBulletin
CVE-2025-53770Exploited in the wildNVD status: Analyzed

Microsoft SharePoint Deserialization of Untrusted Data

Published Updated By the CyberSecBulletin desk

CVE-2025-53770 is a critical-severity deserialization of untrusted data vulnerability in Microsoft SharePoint Enterprise Server 2016 from Microsoft, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists version 16.0.5513.1001 as the first without the flaw, so updating Microsoft SharePoint Enterprise Server 2016 to that release or later removes the exposure. CISA added it to the Known Exploited Vulnerabilities catalogue on July 20, 2025, which means attacks have been observed in the wild, including in ransomware campaigns.

Patch now

Attackers are already exploiting this vulnerability, according to CISA.

What to do

  1. Update Microsoft SharePoint Enterprise Server 2016 to 16.0.5513.1001 or a later version.
  2. Update Microsoft SharePoint Server 2019 to 16.0.10417.20037 or a later version.
  3. Update Microsoft SharePoint Server Subscription Edition to 16.0.18526.20508 or a later version.
  4. CISA's required action: 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.
  5. Read the advisory on msrc.microsoft.com for workarounds and exact fixed builds.
  6. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
MicrosoftMicrosoft SharePoint Enterprise Server 201616.0.0 up to, but not including, 16.0.5513.100116.0.5513.1001
MicrosoftMicrosoft SharePoint Server 201916.0.0 up to, but not including, 16.0.10417.2003716.0.10417.20037
MicrosoftMicrosoft SharePoint Server Subscription Edition16.0.0 up to, but not including, 16.0.18526.2050816.0.18526.20508
MicrosoftSharepoint Serverbefore 16.0.18526.20508; 2016; 201916.0.18526.20508

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (microsoft.com).

Official description

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.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Deserialization of Untrusted Data

The product deserializes untrusted data without sufficiently ensuring that the resulting data will be valid.

How developers prevent this class of flaw

  • If available, use the signing/sealing features of the programming language to assure that deserialized data has not been tainted. For example, a hash-based message authentication code (HMAC) could be used to ensure that data has not been modified.
  • When deserializing data, populate a new object rather than just deserializing. The result is that the data flows through safe input validation and that the functions are safe.
  • Explicitly define a final object() to prevent deserialization.

More Deserialization of Untrusted Data vulnerabilities (CWE-502)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: active, automatable: yes, technical impact: total).
  3. Added to CISA's Known Exploited Vulnerabilities catalogue.
  4. Deadline for US federal agencies to remediate, set by CISA.
  5. Record last changed materially (score, affected products, status or references).

References

Patches and release notes

Other vulnerabilities in Microsoft SharePoint Enterprise Server 2016

All Microsoft SharePoint Enterprise Server 2016 vulnerabilities

Recent Deserialization of Untrusted Data vulnerabilities

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