CVE-2026-27750 Vulnerability Analysis & Exploit Details

CVE-2026-27750 Vulnerability Summary

CVE-2026-27750: 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.

CVE-2026-27750 References

External References

• https://support.avira.com/hc/en-us/articles/360010656158-Current-Avira-versions
• https://www.avira.com/en/internet-security
• https://www.gendigital.com/us/en/contact-us/security-advisories/

CWE Common Weakness Enumeration

CAPEC Common Attack Pattern Enumeration and Classification

• Leveraging Race Conditions via Symbolic Links CAPEC-27 This attack leverages the use of symbolic links (Symlinks) in order to write to sensitive files. An attacker can create a Symlink link to a target file not otherwise accessible to them. When the privileged program tries to create a temporary file with the same name as the Symlink link, it will actually write to the target file pointed to by the attackers' Symlink link. If the attacker can insert malicious content in the temporary file they will be writing to the sensitive file by using the Symlink. The race occurs because the system checks if the temporary file exists, then creates the file. The attacker would typically create the Symlink during the interval between the check and the creation of the temporary file.
• Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions CAPEC-29 This attack targets a race condition occurring between the time of check (state) for a resource and the time of use of a resource. A typical example is file access. The adversary can leverage a file access race condition by "running the race", meaning that they would modify the resource between the first time the target program accesses the file and the time the target program uses the file. During that period of time, the adversary could replace or modify the file, causing the application to behave unexpectedly.

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