CVE-2005-3371
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 · uneditedMultiple interpretation error in AVG 7 7.0.323 allows remote attackers to bypass virus scanning via a file such as BAT, HTML, and EML with an "MZ" magic byte sequence which is normally associated with EXE, which causes the file to be treated as a safe type that could still be executed as a dangerous file type by applications on the end system, as demonstrated by a "triple headed" program that contains EXE, EML, and HTML content, aka the "magic byte bug."
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 confidenceAVG 7.0.323 misidentifies file types based on magic bytes rather than actual content. Attackers embed 'MZ' headers (EXE magic bytes) into BAT, HTML, or EML files, causing the AV to treat them as safe while still allowing execution as dangerous content on end systems.
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= 7.0.323CVSS 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
- Authentication
- None
- Confidentiality
- Partial
- Integrity
- Partial
- Availability
- Partial
AV:N/AC:H/Au:N/C:P/I:P/A:P
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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Verify AVG Antivirus is installedCheck for AVG installation by looking in Program Files for AVG folder, or run 'reg query HKLM\Software\AVG' or 'reg query HKLM\Software\Wow6432Node\AVG' on WindowsAffected if AVG Antivirus is installed on the system
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Identify installed AVG versionOpen AVG interface and navigate to Help > About, or check registry key HKLM\Software\AVG\AVG2006\Version or HKLM\Software\AVG\Setup\settings (varies by install method)Affected if The version reported is exactly 7.0.323
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Confirm legacy version in useIf AVG is present but version cannot be directly verified, search for avg.exe or avgcc.exe and check file properties for version numberAffected if Executable version matches 7.0.323 or falls within the 7.0.3xx pre-7.1 lineage
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Assess file type detection mechanismReview AVG configuration for scanning settings, specifically whether content-based analysis or signature/magic-byte detection is enabled (may require checking logs or configuration files in AVG install directory)Affected if AVG is configured to rely on file extension or header analysis rather than full content inspection for BAT, HTML, and EML files
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Test detection with sample file (if safe environment available)Create a benign test file with .bat extension containing 'MZ' header bytes at the start (magic bytes for EXE), submit to AVG for scanningAffected if AVG fails to detect or flags the file as safe despite MZ headers present
A system is affected if AVG Antivirus version 7.0.323 is installed and relies on magic byte detection without content analysis for BAT, HTML, or EML files.
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 dataUpgrade AVG to a patched version (7.1 or later) that properly analyzes file content beyond magic byte detection; implement additional email gateway scanning and user education to defense-in-depth.
- Consultation2.0 h
- Implementation4.0 h
- Testing2.0 h
- Review / QA1.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $2,560.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2005-3371 — 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-2005-3371 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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