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Out-of-bounds WriteWeakness · CWE-787

CVE-2026-6676

HIGH · 7.8 CVSS v3.1 Published 2026-06-12
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
81/100
Remediation priority · High
No privileges

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 · unedited
Heap buffer out-of-bounds write vulnerability in Avira Antivirus engine when scanning a malformed POSIX tar archive may allow Local Execution of Code or Denial-of-Service of the antivirus engine process. This issue affects Avira Antivirus on Windows, macOS, and Linux for engine builds before 8.3.27.12.

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 confidence

Heap buffer overflow in Avira Antivirus engine's tar archive scanner. When parsing a malformed POSIX tar archive, the engine writes beyond allocated heap memory boundaries, potentially allowing an attacker to achieve code execution or crash the AV process with a malicious archive file.

MitigationUpdate Avira Antivirus engine to version 8.3.27.12 or later. In enterprise environments, verify that automatic updates are enabled and functional across all protected endpoints.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS 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
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H

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 checks

Work through these to decide whether this CVE applies to you.

  1. Verify Avira Antivirus is installed
    Check for Avira processes (Avira.Service.exe on Windows, avguard on Linux, Avira on macOS) or look for Avira installation directories (e.g., C:\Program Files\Avira on Windows, /opt/avira on Linux, /Applications/Avira on macOS)
    Affected if Avira Antivirus is not installed on the system
  2. Determine the Avira engine version
    On Windows: Check the version of Avira.Service.exe or avguard.exe via file properties, or run 'avcenter.exe -v' if available. On Linux: Run 'avgaurd -V' or check /opt/avira/lib/ version files. On macOS: Check the bundle version of Avira Security or run 'productutil' if available.
    Affected if Cannot determine the installed engine version for comparison
  3. Compare engine version to fixed release
    Compare your installed engine version to 8.3.27.12. Versions below 8.3.27.12 are affected. On Windows, the version is typically visible in the Avira user interface under 'Help > About' or in the system tray menu.
    Affected if Installed engine version is below 8.3.27.12
  4. Confirm archive scanning is enabled
    In Avira settings, verify that 'Scan archives' or 'Archive scanning' is enabled in the real-time protection (on-access) and/or on-demand scan configuration. On Linux, check /etc/avira/avira.conf or the profile XML for 'scanarchive' setting.
    Affected if Archive scanning is disabled - the vulnerability would not be triggered during normal scanning operations

The system is affected if Avira Antivirus is installed with an engine version below 8.3.27.12 and archive scanning is enabled, allowing the malformed tar file to be processed during scans.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Update Avira Antivirus engine to version 8.3.27.12 or later. In enterprise environments, verify that automatic updates are enabled and functional across all protected endpoints.

Recommended fix Moderate confidence

Avira Antivirus engine build 8.3.27.12 or later

  1. 1. Identify the current Avira Antivirus engine version installed on the system (Windows, macOS, or Linux).
  2. 2. Navigate to the Avira product settings or about section to view the engine build version.
  3. 3. Download the latest Avira Antivirus product update that includes engine build 8.3.27.12 or later.
  4. 4. Apply the update through the Avira update mechanism or reinstall the product with the latest available version.
  5. 5. Verify the engine has been updated to build 8.3.27.12 or newer by checking the version again.
  6. 6. Test the antivirus by scanning a sample POSIX tar archive to confirm the engine no longer crashes.

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation4.0 h
  • Implementation8.0 h
  • Testing6.0 h
  • Review / QA4.0 h
22.0 hours of engineering $3,860
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-6676 in production — separate from our analysis above.

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What this is

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.

What belongs here
  • Verified mitigations, workarounds, and config changes
  • Version or environment caveats, and links to real fixes
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  • No spam, self-promotion, credentials, or personal data