CVE-2008-5521
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 · uneditedAvira AntiVir 7.9.0.36 and possibly 7.8.1.28, when Internet Explorer 6 or 7 is used, allows remote attackers to bypass detection of malware in an HTML document by placing an MZ header (aka "EXE info") at the beginning, and modifying the filename to have (1) no extension, (2) a .txt extension, or (3) a .jpg extension, as demonstrated by a document containing a CVE-2006-5745 exploit.
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 confidenceAvira AntiVir 7.9.0.36 (and possibly 7.8.1.28) fails to detect malware embedded in HTML documents when an MZ (EXE) header is placed at the beginning of the file and the filename uses no extension, a .txt extension, or a .jpg extension, allowing malicious HTML content containing exploits (such as CVE-2006-5745) to bypass antivirus scanning.
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= 7.8.1.28= 7.9.0.36CVSS 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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Identify Avira AntiVir installationCheck for Avira AntiVir in installed programs list via Control Panel > Programs and Features, or check the installation directory (typically C:\Program Files\Avira\AntiVir Desktop\ or similar)Affected if Avira AntiVir is installed on the system
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Determine installed version numberRight-click the Avira system tray icon and select 'About' or 'Open AntiVir', then locate the version number displayed in the interface. Alternatively, check the version in the program's properties or the setupinf.txt file in the installation folder.Affected if The displayed version matches 7.8.1.28 or 7.9.0.36 exactly
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Verify scanning behavior with disguised HTML filesCreate a test file with an MZ (EXE) header at the beginning, save it with no extension or with .txt or .jpg extension, embed HTML content with script tags, then attempt a manual scan of the file using Avira to see if it detects the HTML contentAffected if Avira fails to detect or flag the HTML content embedded in files with these extensions or no extension when an MZ header is present
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Confirm scan engine is active and updatedCheck Avira's scan engine version and last update date via the product interface to ensure the scanner is functionalAffected if The scan engine is outdated or the virus definitions are severely outdated, compounding the detection failure
A user is affected if they are running Avira AntiVir versions 7.8.1.28 or 7.9.0.36 (Free version) and rely on it to scan HTML files, particularly those with no extension, .txt, or .jpg extensions that contain embedded executable content with MZ headers.
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 Avira AntiVir to a patched version that properly inspects HTML content regardless of file extension or embedded headers, or implement additional endpoint protection and network-based controls to detect malicious HTML exploits.
- Consultation2.0 h
- Implementation4.0 h
- Testing3.0 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 $2,800.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2008-5521 — 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-2008-5521 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
- No spam, self-promotion, credentials, or personal data