CVE-2016-3255
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 · uneditedMicrosoft .NET Framework 2.0 SP2, 3.5, 3.5.1, 4.5.2, 4.6, and 4.6.1 allows remote attackers to read arbitrary files via XML data containing an external entity declaration in conjunction with an entity reference, related to an XML External Entity (XXE) issue, aka ".NET Information Disclosure Vulnerability."
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 · high confidenceThis is an XML External Entity (XXE) injection vulnerability in Microsoft .NET Framework versions 2.0 SP2 through 4.6.1. Attackers can craft malicious XML documents containing external entity declarations to read arbitrary files from the server's filesystem, leading to information disclosure.
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= 2.0= 3.5= 3.5.1= 4.5.2= 4.6= 4.6.1CVSS 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
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- None
- Availability
- None
CVSS:3.0/AV:N/AC:L/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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Determine installed .NET Framework versionRun 'reg query "HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full" /v Version' or check registry at HKLM\SOFTWARE\Microsoft\NET Framework Setup\NDP for the Version valueAffected if The installed version is 2.0, 3.5, 3.5.1, 4.5.2, 4.6, or 4.6.1 (or falls within 2.0 SP2 through 4.6.1)
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Identify XML parsing code in applicationsSearch application source code for usage of System.Xml.XmlReader, XmlDocument, XPathDocument, or other System.Xml classes that process XML inputAffected if Your applications use .NET XML parsing classes to process XML from external or untrusted sources
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Check XmlResolver configuration on XML readersSearch code for XmlReaderSettings.XmlResolver property usage - verify whether it is explicitly set to null or configured with a restricted XmlSecureResolverAffected if XmlResolver is not set to null or a restricted resolver, meaning external entities can be resolved
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Identify XML input sourcesReview where XML input originates - file uploads, API requests, configuration files, or external system integrationsAffected if Your application accepts XML input from untrusted or external sources without sanitization
You are likely affected if your .NET Framework version is between 2.0 and 4.6.1 and your application parses XML with XmlResolver enabled allowing external entity resolution.
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.
From vendor dataDisable external entity resolution in .NET XML parsers by setting XmlReaderSettings.XmlResolver to null or using a custom XmlSecureResolver with restricted permissions, and apply the relevant Microsoft security patch for the affected .NET Framework versions.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2016-3255 — 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-2016-3255 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
- No weaponised exploit code, or anything meant to cause harm
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