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CVE-2025-4134VulnerabilityPublished

CVE-2025-4134: Avast Business Antivirus · Exposed Files or Directories

Affects Avast Business AntivirusSource CVE Database V5

0

Not known to be exploited · CVSS 7.3 High.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score
7.3High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 12% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:3.1/AV:L/AC:L/PR:L/UI:R/S:U/C:H/I:H/A:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 28 May 2025

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-25.

What to do

Affected software

ProductAffectedFixed in
Avast Avast Business AntivirusAffected
  • =4.5.1
Fixed in–

AI-suggested

2) Restrict local user access on Linux systems running Avast Business Antivirus to trusted administrators only, minimizing the risk of unprivileged users exploiting the flaw. 3) Implement strict file system permissions and monitoring on directories used by Avast for updates to detect unauthorized modifications. 4) Employ application whitelisting and integrity verification tools to monitor the update files and binaries for tampering. 5) Conduct regular audits of user accounts and privilege levels to prevent unauthorized local access. 6) Consider deploying additional endpoint detection and response (EDR) solutions that can detect anomalous behavior related to update tampering. 7) Educate system administrators and users about the risks of local privilege misuse and encourage prompt reporting of suspicious activity. These steps go beyond generic advice by focusing on access control hardening, monitoring, and proactive detection tailored to the specific vulnerability context.

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.

References

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