SYSTEM privilege escalation via junction-swapped cleanup path
Published Mar 5, 2026 · Updated Mar 5, 2026
TOCTOU in Avira Internet Security's Optimizer 1.1.109.1990 and earlier allows local users to gain SYSTEM privileges through path swapping. The Optimizer scans a user-controlled directory, then deletes it as SYSTEM without revalidating the path after it is replaced by a junction. Exploitation requires a low-privileged Windows session, a cleanup candidate older than ten minutes, and winning the scan-to-cleanup race; success deletes protected directories and enables a SYSTEM-loaded DLL to be planted.
Summary
What happened
TOCTOU in Avira Internet Security's Optimizer 1.1.109.1990 and earlier allows local users to gain SYSTEM privileges through path swapping. The Optimizer scans a user-controlled directory, then deletes it as SYSTEM without revalidating the path after it is replaced by a junction. Exploitation requires a low-privileged Windows session, a cleanup candidate older than ten minutes, and winning the scan-to-cleanup race; success deletes protected directories and enables a SYSTEM-loaded DLL to be planted.
The record
- CVE
- CVE-2026-27750
- Published
- Mar 5, 2026
- Updated
- Mar 5, 2026
- Vendor
- Gen Digital
- Product
- Avira Internet Security
- Classifications
- CWE-367, T1068
- Attack vector
- local
- Privileges
- authenticated
Timeline
How it unfolded
- Mar 5, 2026CVE publishedPublication date reported by the CVE source.
- Mar 5, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <=1.1.109.1990
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- Quarkslab Optimizer TOCTOU prooffunctional · demonstrated
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Technologies
Your stack
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Your stack
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