# CVE-2025-66631: Csla — Fixed in 6.0.0

.NET NuGet

Not in CISA KEV

# CVE-2025-66631 — Csla

[Fix: MarimerLLC/csla#4018](https://github.com/MarimerLLC/csla/pull/4018)

CVE-2025-66631 is a Deserialization of Untrusted Data vulnerability in Csla. A fix is available for Csla — see the affected versions and patch details below.

CSLA .NET is vulnerable to Remote Code Execution via WcfProxy

Also known as[GHSA-wq34-7f4g-953v](/vulnerability/GHSA-wq34-7f4g-953v)

Published

Dec 9, 2025

Updated

Oct 28, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

## Exploitation Status

### No confirmed exploitation observed yet

-   CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
-   A successful exploit gives an attacker total control of the affected component, not partial access.
-   CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.

Exploitation and automatability from CISA’s SSVC triage for CVE-2025-66631.

## EPSS Exploitation Probability

[via FIRST.org ↗](https://www.first.org/epss/)

0.7%probability of exploitation in next 30 days

Lower Risk+0.05%

Lower risk than most CVEs54th percentile — riskier than 54% of all scored CVEsHighest risk

0.00%1.17%2.33%3.50%1.7%0.7%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/).

## Real-World Exposure

1 pkg affected

.NET`Csla`

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.

## Description

#### Impact

Versions of CSLA .NET prior to version 6 allow the use of WcfProxy. WcfProxy uses the NetDataContractSerializer (NDCS) which has known vulnerabilities that can allow remote execution of code during deserialization. NDCS itself is considered obsolete, and you should avoid using WcfProxy or upgrade to CSLA 6 or higher where this issue does not exist.

#### Patches

CSLA .NET version 6 and higher do not use WCF or NetDataContractSerializer.

#### Workarounds

If you are using a version CSLA .NET older than version 6, you should stop using WcfProxy in your data portal configuration. Doing this avoids the use of WCF and the NetDataContractSerializer, avoiding the vulnerability.

## Affected Packages

1 total 1 fixed

Ecosystem

Package

Vulnerable range

Fix

.NETNuGet

`Csla` 

all versions

6.0.0`dotnet add package Csla --version 6.0.0`

## Affected Products

1 product · 1 configurations

Application

`csla .net`cslanet

< 6.0.0

range

## Detection & mitigation playbook

Open-source dependency

1.  ### Detect
    
    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for Csla, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
    
2.  ### Fix
    
    Update Csla to 6.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-66631 is resolved across your whole dependency graph.
    
3.  ### Workarounds
    
    Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.
    

## Frequently Asked Questions

\### Impact Versions of CSLA .NET prior to version 6 allow the use of WcfProxy. WcfProxy uses the NetDataContractSerializer (NDCS) which has known vulnerabilities that can allow remote execution of code during deserialization. NDCS itself is considered obsolete, and you should avoid using WcfProxy or upgrade to CSLA 6 or higher where this issue does not exist. ### Patches CSLA .NET version 6 and higher do not use WCF or NetDataContractSerializer. ### Workarounds If you are using a version CSLA .NET older than version 6, you should stop using WcfProxy in your data portal configuration. Doing t

O3 Security · Impact-Aware SCA

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