Avast Antivirus, Avast One, Avast Premium…: Unrestricted Upload of File with Dangerous Type
CVE-2026-80302 is a high-severity unrestricted upload of file with dangerous type vulnerability in Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate from Gen Digital, with a CVSS 3.1 base score of 8.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists version 26.7 as the first without the flaw, so updating Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.13% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate to 26.7 or a later version.
- Update AVG Antivirus Free, AVG Internet Security, AVG Ultimate to 26.7 or a later version.
- Update Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced to 26.7 or a later version.
- Read the advisory on gendigital.com for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Gen Digital | Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate | before 26.7 | 26.7 |
| Gen Digital | AVG Antivirus Free, AVG Internet Security, AVG Ultimate | before 26.7 | 26.7 |
| Gen Digital | Norton Antivirus Plus, Norton 360 Standard, Norton 360 Deluxe, Norton 360 Advanced | before 26.7 | 26.7 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H. Scored by CISA (ADP).
Official description
Insufficient isolation in the Avast sandbox file virtualization layer on Windows allows a local, low-privileged attacker executing inside the sandbox to write arbitrary files outside sandbox containment and execute code on the host. The sandbox virtualizes file system operations by intercepting write requests to protected system directories. However, the virtualization implementation fails to properly validate write targets in certain edge cases, allowing writes to bypass the virtualization redirection and reach the actual host file system in protected locations. An attacker can exploit this to overwrite executable files, system libraries, or startup configurations with arbitrary content, leading to code execution with host privileges on subsequent system operations or reboot.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Unrestricted Upload of File with Dangerous Type
The product allows the upload or transfer of dangerous file types that are automatically processed within its environment.
How developers prevent this class of flaw
- Generate a new, unique filename for an uploaded file instead of using the user-supplied filename, so that no external input is used at all.
- When the set of acceptable objects, such as filenames or URLs, is limited or known, create a mapping from a set of fixed input values (such as numeric IDs) to the actual filenames or URLs, and reject all other inputs.
- Consider storing the uploaded files outside of the web document root entirely. Then, use other mechanisms to deliver the files dynamically.
More Unrestricted Upload of File with Dangerous Type vulnerabilities (CWE-434)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Other references
Other vulnerabilities in Avast Antivirus, Avast One, Avast Premium Security, Avast Ultimate
- 8.8 High severity
Recent Unrestricted Upload of File with Dangerous Type vulnerabilities
- 8.1 High severity
- 10.0 Critical severity
- 9.0 Critical severity
- 7.2 High severity
- 8.8 High severity
- 9.8 Critical severity
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