CVE-2025-6444
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedServiceStack GetErrorResponse Improper Input Validation NTLM Relay Vulnerability. This vulnerability allows remote attackers to relay NTLM credentials on affected installations of ServiceStack. Interaction with this library is required to exploit this vulnerability but attack vectors may vary depending on the implementation. The specific flaw exists within the implementation of the GetErrorResponse method. The issue results from the lack of proper validation of user-supplied data, which can result in a type confusion condition. An attacker can leverage this vulnerability to relay NTLM credentials in the context of the current user. Was ZDI-CAN-25834.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceThis vulnerability exists in ServiceStack's GetErrorResponse method, which fails to properly validate user-supplied data, leading to a type confusion condition. Attackers can exploit this improper input validation to relay NTLM credentials in the context of the current user. The vulnerability requires interaction with the ServiceStack library but the attack vector may vary based on implementation.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 8.6CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- High
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify ServiceStack installationSearch for ServiceStack DLLs (ServiceStack.dll, ServiceStack.Core.dll) in application bin directories, or check NuGet package references in project files (.csproj, packages.config)Affected if ServiceStack libraries are found in the application
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Determine installed ServiceStack versionRight-click ServiceStack.dll and view Properties > Details > File Version, or check the version in NuGet package manager or .csproj fileAffected if Version is lower than 8.6.0 or the version cannot be determined and is assumed to be older
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Check if web endpoints expose ServiceStackReview application routing configuration and web.config/.csproj for ServiceStack routes (typically paths like /api, /servicestack, or custom routes using .RegisterServiceStack() or app.UseServiceStack() )Affected if ServiceStack HTTP endpoints are publicly accessible
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Verify NTLM authentication is enabledCheck web.config or application settings for authentication modes: look for <authentication mode="Windows"> and verify NTLM authentication is not disabled via registry or IIS configuration (NTLM provider is listed in authentication providers)Affected if Windows authentication with NTLM is enabled and the application runs under a Windows account with network privileges
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Inspect GetErrorResponse method usageSearch application code for calls to GetErrorResponse method or review if custom error handlers in ServiceStack are implemented that could invoke this method during exception processingAffected if Custom error handling or exception logging that invokes GetErrorResponse is in use
The environment is affected if ServiceStack version is below 8.6.0, ServiceStack web endpoints are accessible, and NTLM authentication is enabled, allowing potential credential relay via the GetErrorResponse method.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped8.6
Implement proper input validation in the GetErrorResponse method to prevent type confusion. Additionally, mitigate NTLM relay by enabling SMB signing or disabling NTLM authentication in favor of Kerberos where possible.
ServiceStack 8.6
- 1. Identify the current ServiceStack version in use by checking project references, NuGet packages, or the deployed binaries
- 2. Backup the current project and any deployed applications before making changes
- 3. Update ServiceStack to version 8.6 or later by running 'Update-Package ServiceStack' or modifying the .csproj file with the new version number
- 4. Rebuild the application to ensure compatibility with the new ServiceStack version
- 5. Test the application thoroughly, particularly error handling paths that utilize GetErrorResponse
- 6. Deploy the updated application to production
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 h
- Review / QA2.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-6444 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-6444 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
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