Raw vector
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:HCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2026-27750 is a high-severity Time-of-check Time-of-use (TOCTOU) Race Condition (CWE-367) vulnerability in Avira Internet Security. Its CVSS base score is 7.8 (High).
Operationally, exploitation aligns with the MITRE ATT&CK technique Path Interception (T1034); ranked at the 3th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.
The strongest mitigations our analysis identified map to AC-25 (Reference Monitor) and AC-3 (Access Enforcement) — see the control section below for these in your framework.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
CVE-2026-27750 is a time-of-check time-of-use (TOCTOU) vulnerability in the Optimizer component of Avira Internet Security. A privileged service running as SYSTEM identifies directories for cleanup during a scan phase and deletes them in a subsequent cleanup phase without revalidating the target path. This affects Avira Internet Security products, with a CVSS v3.1 base score of 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) and is associated with CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition).
A local attacker with low privileges can exploit this vulnerability by replacing a previously scanned directory with a junction or reparse point before the deletion phase. This causes the privileged process to delete an unintended system location, potentially resulting in the removal of protected files or directories. Depending on the targeted location, outcomes may include local privilege escalation, denial of service, or system integrity compromise.
Vendor advisories provide mitigation guidance, including updates to current Avira versions, as detailed on the Avira support page (https://support.avira.com/hc/en-us/articles/360010656158-Current-Avira-versions), the Avira Internet Security product page (https://www.avira.com/en/internet-security), and Gen Digital security advisories (https://www.gendigital.com/us/en/contact-us/security-advisories/).
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2026-9822
Vulnerability Data
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…
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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.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V15.4.2V17.2.6
Mitigating Controls (NIST 800-53 r5) AI
A reference monitor that is always invoked and analyzable structurally eliminates the non-atomic check-then-use pattern underlying TOCTOU.
Access enforcement that performs an atomic check-and-use decision directly stops the window in which a TOCTOU race can be exploited.
Process isolation limits the blast radius of a successful TOCTOU exploitation but does not remove the race itself.
Mitigating Controls (NIST CSF 2.0) AI
Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.
Secure SDLC practices directly include coding standards and reviews that prevent TOCTOU race conditions.