CyberSecBulletin
CVE-2025-4134NVD status: Deferred

Avast Business Antivirus: Files or Directories Accessible to External Parties

Published Updated By the CyberSecBulletin desk

CVE-2025-4134 is a high-severity files or directories accessible to external parties vulnerability in Avast Business Antivirus from Avast, with a CVSS 3.1 base score of 7.3 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, but only if a user takes part, for example by opening a link or file. Affected Avast Business Antivirus versions: 4.5.1. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.22% chance of exploitation within 30 days, which is low compared with other CVEs.

Next patch cycle

High severity with no evidence of exploitation so far.

What to do

  1. Check which version of Avast Business Antivirus you run against the affected versions below, and install the vendor's latest release.
  2. Read the advisory on gendigital.com for workarounds and exact fixed builds.
  3. Because the attack needs a user to take part, warn users about unexpected links and files related to this product until it is patched.

Affected products and versions

VendorProductAffected versionsFixed in
AvastAvast Business Antivirus4.5.1Not stated

Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
LocalThe attacker needs local access or must trick a user into running something.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
LowA basic user account is enough.
User interaction
RequiredA user must take an action such as opening a file or link.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
HighAll data handled by the component can be read.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H. Scored by CNA (nortonlifelock.com).

Official description

Lack of file validation in do_update_vps in Avast Business Antivirus for Linux 4.5 on Linux allows local user to spoof or tamper with the update file via an unverified file write.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Files or Directories Accessible to External Parties

The product makes files or directories accessible to unauthorized actors, even though they should not be.

How developers prevent this class of flaw

  • When storing data in the cloud (e.g., S3 buckets, Azure blobs, Google Cloud Storage, etc.), use the provider's controls to disable public access.

More Files or Directories Accessible to External Parties vulnerabilities (CWE-552)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
  3. Record last changed materially (score, affected products, status or references).

References

Recent Files or Directories Accessible to External Parties vulnerabilities

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