CVE-2025-66631Network attack vector

Remote code execution via unsafe WcfProxy deserialization

Published Dec 9, 2025 · Updated Dec 9, 2025

Unsafe deserialization in WcfProxy in Marimer LLC CSLA .NET before 6.0.0 allows remote attackers to execute arbitrary code. WcfProxy passes untrusted object data to NetDataContractSerializer, which accepts unexpected .NET types with malicious side effects during deserialization. Exposure requires an application to configure the legacy WcfProxy data portal, and resulting code runs with the hosting process's privileges.

CVSS severity9.8
Critical
EPSS probability0.67%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Unsafe deserialization in WcfProxy in Marimer LLC CSLA .NET before 6.0.0 allows remote attackers to execute arbitrary code. WcfProxy passes untrusted object data to NetDataContractSerializer, which accepts unexpected .NET types with malicious side effects during deserialization. Exposure requires an application to configure the legacy WcfProxy data portal, and resulting code runs with the hosting process's privileges.

The record

CVE
CVE-2025-66631
Published
Dec 9, 2025
Updated
Dec 9, 2025
Vendor
Marimer LLC
Product
CSLA .NET
Classifications
CWE-502, T1190
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Dec 9, 2025CVE publishedPublication date reported by the CVE source.
  2. Dec 9, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 6.0.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Marimer LLC · CSLA .NETversion=< 6.0.0

Published CVSS scores

7.2GitHub, Inc.CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:U/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-502Deserialization of Untrusted Data
T1190Exploit Public-Facing Application

Public exploit references

No public exploit references are available in this record.

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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