CVE-2020-25289

The VPN service in AVAST SecureLine before 5.6.4982.470 allows local users to write to arbitrary files via an Object Manager symbolic link from the log directory (which has weak permissions).

Weakness

The product attempts to access a file based on the filename, but it does not properly prevent that filename from identifying a link or shortcut that resolves to an unintended resource.

Affected Software

Potential Mitigations

• Follow the principle of least privilege when assigning access rights to entities in a software system.
• Denying access to a file can prevent an attacker from replacing that file with a link to a sensitive file. Ensure good compartmentalization in the system to provide protected areas that can be trusted.

Related Attack Patterns

• https://cwe.mitre.org/data/definitions/132.html
• https://cwe.mitre.org/data/definitions/17.html
• https://cwe.mitre.org/data/definitions/35.html
• https://cwe.mitre.org/data/definitions/76.html

References

• http://zeifan.my/security/arbitrary%20file/eop/2020/07/21/avast-secureline-vpn-arb-file-eop.html