CVE-2012-4776
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 · uneditedThe Web Proxy Auto-Discovery (WPAD) functionality in Microsoft .NET Framework 2.0 SP2, 3.5, 3.5.1, 4, and 4.5 does not validate configuration data that is returned during acquisition of proxy settings, which allows remote attackers to execute arbitrary JavaScript code by providing crafted data during execution of (1) an XAML browser application (aka XBAP) or (2) a .NET Framework application, aka "Web Proxy Auto-Discovery 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 confidenceThe Web Proxy Auto-Discovery (WPAD) functionality in Microsoft .NET Framework 2.0 SP2 through 4.5 does not validate configuration data returned during proxy settings acquisition, allowing remote attackers to inject and execute arbitrary JavaScript code by providing crafted data through XBAP or .NET applications.
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= 3.5.1= 4.0= 3.5= 4.5CVSS 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
- M
- Authentication
- None
- Confidentiality
- Complete
- Integrity
- Complete
- Availability
- Complete
AV:N/AC:M/Au:N/C:C/I:C/A:C
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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Check installed .NET Framework versionOpen Registry Editor and navigate to HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v4\Full (for .NET 4.x) or HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\NET Framework Setup\NDP\v2\v3.5 (for older versions). Look for the 'Version' value in the appropriate subkey.Affected if The installed version falls within .NET Framework 2.0 SP2 through 4.5 (versions 2.0, 3.5, 3.5.1, 4.0, or 4.5).
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Verify if WPAD is enabled in Internet ExplorerOpen Internet Explorer, go to Tools > Internet Options > Connections > LAN settings. Check if the 'Automatically detect settings' checkbox is enabled.Affected if The 'Automatically detect settings' option is checked, which enables WPAD functionality.
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Check system-wide proxy auto-detection settingsOpen Command Prompt and run: netsh winhttp show proxy. This displays the WinHTTP proxy configuration.Affected if The output shows 'Auto-detect' or indicates that proxy settings are set to automatically detect, meaning WPAD is in use.
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Identify if .NET applications use System Proxy settingsReview application configuration files and code that uses System.Net.WebRequest.DefaultWebProxy or WebProxy.GetDefaultProxy to determine if proxy auto-detection is invoked.Affected if The .NET application or XBAP is configured to use system proxy settings, which would invoke WPAD.
A system is affected if it runs a vulnerable .NET Framework version (2.0 SP2 through 4.5) AND has WPAD/auto-detect proxy settings enabled, allowing .NET applications or XBAP to automatically retrieve proxy configuration.
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 dataApply Microsoft's security update for this vulnerability (MS12-074) or disable WPAD at the system level and configure explicit proxy settings.
- 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-2012-4776 — 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-2012-4776 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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A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.
- 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
- No spam, self-promotion, credentials, or personal data