Avira Internet Security contains a time-of-check time-of-use (TOCTOU) vulnerability in the Optimizer component. A privileged service running as SYSTEM identifies directories for cleanup during a scan phase and subsequently deletes them during a separate cleanup phase without revalidating the target path. A local attacker can replace a previously scanned directory with a junction or reparse point before deletion occurs, causing the privileged process to delete an unintended system location.
This may result in deletion of protected files or directories and can lead to local privilege escalation, denial of service, or system integrity compromise depending on the affected target.
Attack Parameters
Attack Vector
Local
Requires local access
Attack Complexity
Low
Easy to exploit
Attack Requirements
None
No additional conditions
Privileges Required
Low
Basic privileges needed
User Interaction
None
No user interaction needed
Impact Assessment
Confidentiality
High
Complete data leak
Integrity
High
Complete data modification
Availability
High
Complete denial of service
CVSS Vector v4.0
Weakness Type (CWE)
References 4
https://blog.quarkslab.com/avira-deserialize-delete-and-escalate-the-proper-way…
disclosure@vulncheck.com
https://support.avira.com/hc/en-us/articles/360010656158-Current-Avira-versions
disclosure@vulncheck.com
https://www.avira.com/en/internet-security
disclosure@vulncheck.com
https://www.vulncheck.com/advisories/avira-internet-security-optimizer-toctou
disclosure@vulncheck.com