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Heap-based Buffer OverflowWeakness · CWE-122

CVE-2025-8351

HIGH · 7.8 CVSS v3.1 Published 2025-12-01
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-based Buffer Overflow, Out-of-bounds Read vulnerability in Avira Antivirus engine when scanning a malformed file 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 8.3.70.98.

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

A heap-based buffer overflow and out-of-bounds read vulnerability exists in the Avira Antivirus scanning engine when processing malformed files. An attacker can trigger this vulnerability by presenting a specially crafted file to the antivirus for scanning, potentially achieving local code execution with the privileges of the antivirus engine process or causing a denial of service by crashing the engine.

MitigationUpdate Avira Antivirus engine to version 8.3.70.98 or later across all affected platforms (Windows, macOS, Linux) to remediate this vulnerability.

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
    Search for Avira installation. On Windows: check Program Files/Avira folder and Registry keys under HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall. On macOS: check /Applications for Avira icons. On Linux: run 'dpkg -l | grep -i avira' or 'rpm -qa | grep -i avira'.
    Affected if No Avira product found - not affected by this CVE
  2. Determine the Avira engine version
    On Windows: open Avira Control Center > Help > About, or check avgnt.exe/avscan.exe properties in the installation folder. On macOS: right-click Avira app > Get Info. On Linux: run 'avupdate' or check version files in /opt/avira/.
    Affected if Unable to determine version - further investigation required
  3. Compare installed version to affected range
    Compare the identified version number to the fixed version 8.3.70.98. Any version below 8.3.70.98 (including 8.3.70.x versions below 98, 8.2.x, 8.1.x, older major versions) falls within the affected range.
    Affected if Installed version is below 8.3.70.98 - vulnerable to this CVE
  4. Confirm scanning features are active
    Check if Avira real-time protection, scheduled scans, or on-demand scanner is enabled. On Windows: open Avira Security app and verify Protection status. On macOS: check Avira > Preferences > Protection. On Linux: check avguard service with 'systemctl status avguard'.
    Affected if Engine is installed but no scanning features are ever used, exposure is minimal but the vulnerable code is still present

If Avira Antivirus is installed with a version lower than 8.3.70.98 and scanning features are or could be activated, the environment is affected by CVE-2025-8351.

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 8.3.70.98 or later across all affected platforms (Windows, macOS, Linux) to remediate this vulnerability.

Recommended fix High confidence

Avira Antivirus engine build 8.3.70.98 or later

  1. Open Avira Antivirus application on your Windows, macOS, or Linux system
  2. Navigate to the Update or Settings section within the application
  3. Trigger a manual engine update or allow automatic updates to run
  4. Verify the engine build version has reached 8.3.70.98 or later after the update completes
  5. Confirm the update was successful by checking the antivirus engine version in the About or Help section

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

Have this fixed Scoped from the published advisory
  • Consultation1.0 h
  • Implementation2.0 h
  • Testing1.0 h
  • Review / QA1.0 h
5.0 hours of engineering $890
Get help mitigating

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Scan for this in your stack

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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-2025-8351 in production — separate from our analysis above.

No notes yet

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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
  • No weaponised exploit code, or anything meant to cause harm
  • No spam, self-promotion, credentials, or personal data