CVE-2020-9399
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 Avast AV parsing engine allows virus-detection bypass via a crafted ZIP archive. This affects versions before 12 definitions 200114-0 of Antivirus Pro, Antivirus Pro Plus, and Antivirus for Linux.
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 confidenceThe Avast AV parsing engine fails to properly detect malicious content within crafted ZIP archives, allowing malware to bypass virus detection. This is a logic flaw in the archive parsing component that can be exploited by specially crafted ZIP files.
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< 12.0< 12.0< 12.0CVSS 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
- Local
- Complexity
- Low
- Privileges
- None
- User interaction
- Required
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/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.
-
Identify installed Avast productRun command: 'dpkg -l | grep -i avast' or 'rpm -qa | grep -i avast' to list installed Avast packagesAffected if No Avast package is found, the system is not affected by this specific vulnerability
-
Get Avast engine versionRun command: 'avast --version' or check the about/version information in the Avast GUI if availableAffected if Unable to retrieve version information - product may be too old or installation is incomplete
-
Compare version against affected rangeCheck if the installed version is below 12.0 (e.g., 11.x, 10.x, etc.)Affected if Version is below 12.0 - the parsing engine logic flaw exists and crafted ZIP files may bypass detection
-
Verify ZIP archive scanning is enabledCheck Avast settings to confirm archive scanning (ZIP, RAR, etc.) is enabled in the real-time or on-demand scanner configurationAffected if Archive scanning is disabled, the specific parsing logic flaw is not reachable but the product is still vulnerable if enabled later
-
Confirm definitions date as secondary checkIf version is 12.0 or later but definitions are older than 200114-0, the logic flaw may still be present in the engineAffected if Definitions are pre-200114-0 despite version 12 - the vulnerability may still be exploitable
The system is affected if Avast Antivirus for Linux, Pro, or Pro Plus is installed with a version lower than 12.0 and ZIP archive scanning is enabled.
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 data12.0
Update Avast Antivirus Pro, Antivirus Pro Plus, or Antivirus for Linux to version 12 definitions 200114-0 or later to remediate the vulnerability.
- 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-2020-9399 — 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-2020-9399 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
Be the first to add a field note for this CVE — a mitigation you’ve verified, a version caveat, or a link to a working fix. Sign in above to contribute.
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